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1
Maslen, Paul E. "Anharmonic potential energy surfaces". Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240073.
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Mort, Steven P. "Potential energy surfaces for SiHâ†2+". Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240482.
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3
Bholoa, Ajeevsing. "Potential energy surfaces using neural networks". Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/35257.
Testo completoAbstract (sommario):
A neural network is developed to fit a potential energy surface of silicon derived from Frauenheim tight-binding data for silicon. The tight-binding method retains the essentials of quantum mechanics for electronic structure calculations but is faster to calculate than a full ab initio model. The development of the neural network potential energy surface was carried out by a progressive refinement of the design parameters. The refinement of the models went hand in hand with the difficulty encountered in developing a transferable network potential. Both equilibrium and non-equilibrium parts of the potential energy surface were represented in the training data set. The neural network potential was fitted on dimers, linear and angled trimers, tetramers, diamond structures, distorted diamond lattice systems, and the BC8, ST12, BCT5 and β-tin structures.
4
Merritt, Jeremy Miles Baer Tomas. "Spectroscopic probes of reactive potential energy surfaces". Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2006. http://dc.lib.unc.edu/u?/etd,385.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2006.Title from electronic title page (viewed Oct. 10, 2007). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry." Discipline: Chemistry; Department/School: Chemistry.
5
Rempe, Susan Lynne Beamis. "Potential energy surfaces for vibrating hexatomic molecules /". Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/8536.
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6
Howson, Joanna M. M. "Obtaining potential energy surfaces of Van der Waals molecules". Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4488/.
Testo completoAbstract (sommario):
Two different methods were used to obtain a potential energy surface for the Arco molecule. One involved choosing a functional form for the repulsion and dispersion energies whose parameters were determined by a fit to experimental data. A physically justified potential that agreed with experiment could not be obtained. The other method was based on calculating ab initio interaction energies at different configurations of the molecule and interpolating between them. The resulting surface was scaled in the energy and the co-ordinates. Improved agreement was achieved for most observed bound states. Errors in the surface may have been due to an inadequate density of ab initio energies. So, how the molecular configurations chosen for interaction energy calculations affected the potential obtained was investigated. Both the co-ordinate system and the interpolation scheme also significantly affected the quality of surface obtained. The best compromise between accuracy and number of configurations, was points distributed on a regular grid in elliptic co-ordinates with Gauss-Legendre quadrature points in the angular co-ordinate. This information was employed to obtain a potential energy surface for the weakly bound HeOCS molecule which was in close agreement with experiment. A co-ordinate and energy scaling, guided by experiment, was applied to the ab initio surface. Only three scaling parameters were required due to the high quality of the initial surface.
7
Kain, Jacqueline Sophie. "Constructing ab initio and empirical potential energy surfaces for water". Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248404.
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8
Craven, W. A. "Potential energy surfaces and molecular dynamics of sulphur-oxygen systems". Thesis, University of Sussex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372715.
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9
Chen, Yizhou. "Adhesion of Spider Glue on Different Surface Energy and Surface Potential Surfaces". University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1462227997.
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10
Reeves, Christopher Thomas. "Kinetics and dynamics of adsorption on single crystal semiconductor and metal surfaces". Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3035962.
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Mann, Jennifer Erin. "Probing the potential energy surfaces of elementary neutral reactions using dissociative charge exchange". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3335027.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of California, San Diego, 2008.Title from first page of PDF file (viewed December 5, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
12
Joo, Hyun. "Exploring potential energy sources and reaction mechanisms of inorganic molecules by computational methods". Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Fall/Dissertation/JOO_HYUN_55.pdf.
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13
Ruiz-Barragán, Sergi. "Modelling of potential energy surfaces for photochemistry: conical intersections and application to optical control". Doctoral thesis, Universitat de Girona, 2014. http://hdl.handle.net/10803/283964.
Testo completoAbstract (sommario):
Conical Intersections (CI) are points in Potential Energy Surfaces (PES) of two or more states that have the same energy. They are fundamental to understand photo-chemical processes. These points are not isolated points, CI form seam between PES. One way to study they is to find the minimum energy CI (MECI). For this reason, in this thesis, a new algorithm for finding MECI has been proposed: Double Newton-Raphson (DNR). The algorithm has been implemented in Gaussian® program for fully-quantum calculations and ONIOM ones. It has been tested with other algorithms with a test set with correct results. Using studies of PES and MECI is possible to propose new strategies for control photo-processes. In this thesis, a new control strategy has been proposed for controlling the fulvene photo-rotation, using two different lasers, resonant and non-resonant, to obtain a Stark effect. This strategy has been simulated with quantum molecular dynamics. The simulations show that the control is achievedLes Interseccions Conques (CI) són punt en la Superfícies d'Energia Potencial (PES) de dos o més estats amb la mateixa energia. Son essencials per entendre els processos fotoquímics. Aquest punts no estan aïllats, les CI formen interseccions entre les PES. Una manera d'estudiar-los és trobant els mínims d'energia (MECI). Per aquest motiu, en aquesta tesis, un nou algoritme ha estat proposat: Double Newton-Raphson (DNR). El DNR ha estat implementat en el programa Gaussian® per càlculs totalment quàntics i ONIOM. Aquest ha estat provat juntament amb altres algoritmes amb un test set amb correctes resultats. Utilitzant els estudis de la PES i els MECI és possible proposar noves estratègies per controlar foto-reaccions. En aquesta tesis, una nova estratègia de control ha estat proposada per tal de controlar la foto-rotació del fulvè, utilitzant dos làsers diferents, un ressonant i un altre no-ressonant per obtenir un efecte Stark. Aquesta estratega ha estat simulada amb dinàmiques moleculars quàntiques. Les simulacions mostres que s'aconsegueix el control
14
Yang, Juan. "Spectroscopic investigations of the vibrational potential energy surfaces in electronic ground and excited states". Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/5900.
Testo completoAbstract (sommario):
The vibrational potential energy surfaces in electronic ground and excited states of several ring molecules were investigated using several different spectroscopic methods, including far-infrared (IR), Raman, ultraviolet (UV) absorption, fluorescence excitation (FES), and single vibronic level fluorescence (SVLF) spectroscopies. Based on new information obtained from SVLF and millimeter wave spectra, the far-IR spectra of coumaran were reassigned and the one-dimensional ring-puckering potential energy functions for several vibrational states in the S0 ground state were determined. The barrier was found to be 154 cm-1 and the puckering angles to be ñ 25ð, in good agreement with the millimeter wave barrier of 152 cm-1 and puckering angles of ñ 23ð. Moreover, the UV absorption and FES spectra of coumaran allowed the one-dimensional ring-puckering potential energy functions in the S1 excited state to be determined. The puckering barrier is 34 cm-1 for the excited state and the puckering angles are ñ 14ð. Several calculations with different basis sets have been carried out to better understand the unusual vibrational frequencies of cyclopropenone. It was shown that there is strong interaction between the C=O and symmetric C-C stretching vibrations. These results differ quantitatively from a previous normal coordinate calculation and interpretation. The vapor-phase Raman spectrum of 3,7-dioxabicyclo[3.3.0]oct-1,5-ene was analyzed and compared to the predicted spectrum from DFT calculations. The spectrum further shows it has D2h symmetry, in which the skeletons of both rings are planar. The infrared and Raman spectra of vapor-phase and liquid-phase 1,4-benzodioxan and 1,2,3,4-tetrahydronaphthalene were collected and the complete vibrational assignments for both molecules were made. Theoretical calculations predicted the barriers to planarity to be 4809 cm-1 for 1,2,3,4-tetrahydonaphthalene and 4095 cm-1 for 1,4-benzodioxan. The UV absorption, FES, and SVLF spectra of both molecules were recorded and assigned. Both one and two-dimensional potential energy functions of 1,4-benzodioxan for the ring-twisting and ring-bending vibrations were carried out for the S0 and S1(ÃÂ,ÃÂ*) states, and these were consistent with the high barriers calculated for both states. The low-frequency spectra of 1,2,3,4-tetrahydronaphthalene in both S0 and S1(ÃÂ,ÃÂ*) states were also analyzed.
15
Daud, Mohammad Noh. "Quantum mechanical study of the potential energy surfaces and photodissociation dynamics of Nâ‚‚O". Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425078.
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Qawasmeh, Yasmeen Jamal [Verfasser]. "Two-Dimensional Potential Energy Surfaces of Binding CO/NO with Coinage Metals / Yasmeen Qawasmeh". Berlin : Freie Universität Berlin, 2020. http://d-nb.info/1212435400/34.
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Zhong, Meili. "Kinetics, potential energy surfaces, and structure-reactivity relationships of gas phase ion molecule reactions. /". May be available electronically:, 1997. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Qawasmeh, Yasmeen [Verfasser]. "Two-Dimensional Potential Energy Surfaces of Binding CO/NO with Coinage Metals / Yasmeen Qawasmeh". Berlin : Freie Universität Berlin, 2020. http://d-nb.info/1212435400/34.
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Mordaunt, David H. "Photodissociation dynamics of small atmospherically important molecules". Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388430.
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Stevenson, Kip Patrick. "Anisotropic potential energy surfaces for atmospheric gas : unsaturated hydrocarbon molecule interactions from differential scattering experiments /". Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/11613.
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Rohrdanz, Mary A. "Intermolecular communication via lattice phonons, probed by ultrafast spectroscopy /". view abstract or download file of text, 2005. http://wwwlib.umi.com/cr/uoregon/fullcit?p3190543.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Oregon, 2005.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 79-80). Also available for download via the World Wide Web; free to University of Oregon users.
22
Atahan, Sule. "Potential energy surfaces and reaction dynamics studies of small triatomic systems O+H2, OH+H and OH+D /". College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3463.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Maryland, College Park, 2006.Thesis research directed by: Chemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
23
Jitariu, Luminita Carmen. "Theoretical study of potential energy surfaces for reactions of the NOâ†3 radical with small radicals in the atmosphere". Thesis, University of Warwick, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340635.
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Stedl, Todd Robert. "Computational investigations of the dynamics of chlorine dioxide /". Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/8497.
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Deskevich, Michael. "Large amplitude quantum mechanics in polyatomic hydrides and multistate electronic potential energy surfaces of highly electronegative fluorine + polyatomic hydride reactive systems". Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3288866.
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Koczor-Benda, Zsuzsanna [Verfasser], e Thomas-Christian [Akademischer Betreuer] Jagau. "Analytic gradient techniques for investigating the complex-valued potential energy surfaces of electronic resonances / Zsuzsanna Koczor-Benda ; Betreuer: Thomas-Christian Jagau". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2019. http://d-nb.info/1180981936/34.
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Alexander, William Andrew. "Theoretical and experimental studies of energy transfer dynamics in collisions of atomic and molecular species with model organic surfaces". Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/26857.
Testo completoAbstract (sommario):
A full understanding of chemical reaction dynamics at the gas/organic-surface interface requires knowledge of energy-transfer processes that happen during the initial gas/surface collision. We have examined the influence of mass and rovibrational motion on the energy-transfer dynamics of gas-phase species scattering from model organic surfaces using theory and experiment. Molecular-beam scattering techniques were used to investigate the rare gases, Ne, Ar, Kr, and Xe, and the diatomics, N2 and CO, in collisions with CH3- and CF3-terminated self-assembled monolayer (SAM) surfaces. Complementary molecular-dynamics simulations were employed to gain an atomistic view of the collisions and elucidate mechanistic details not observable with our current experimental apparatus. We developed a systematic approach for obtaining highly accurate analytic intermolecular potential-energy surfaces, derived from high-quality ab initio data, for use in our classical-trajectory simulations. Results of rare gas scattering experiments and simulations indicate mass to be the determining factor in the energy-transfer dynamics, while other aspects of the potential-energy surface play only a minor role. Additionally, electronic-structure calculations were used to correlate features of the potential-energy surface with the energy-transfer behavior of atoms and small molecules scattering from polar and non-polar SAM surfaces. Collisions of diatomic molecules with SAMs are seen to be vibrationally adiabatic, however translational energy transfer to and from rotational modes of the gas species, while relatively weak, is readily apparent. Examination of the alignment and orientation of the final rotational angular momentum of the gas species reveals that the collisions induce a stereodynamic preference for the expected "cartwheel" motion, as well as a surprising propensity for "corkscrew" or "propeller" motion. The calculated stereodynamic trends suggest that the CH3-SAM is effectively more corrugated than the CF3-SAM. Finally, the feasibility for collisional-energy promoted, direct gas/organic-surface reactions was interrogated using the 1,3-dipolar azide-alkyne cycloaddition reaction. We found that geometrical constraints prevented the reaction from proceeding at the probed conditions.Ph. D.
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Kalugina, Yulia. "Theoretical investigation of the potential energy, dipole moment and polarizability surfaces of the CH4 - N2 and C2H4 - C2H4 van der Waals complexes". Phd thesis, Université de Bourgogne, 2010. http://tel.archives-ouvertes.fr/tel-00621218.
Testo completoAbstract (sommario):
In the present thesis both ab initio and analytical calculations were carried out for thepotential energy, dipole moment and polarizability surfaces of the weakly bound van der Waals complexes CH4-N2 and C2H4-C2H4 for a broad range of intermolecular separations and configurations in the approximation of the rigid interacting molecules. For ab initio calculations the CCSD(T), CCSD(T)-F12 and less computationally expensive methods such as MP2, MP2-F12, SAPT, DFT-SAPT were employed (for all methods the aug-cc-pVTZ basis set was used). The BSSE correction was taken into account during the calculations. The analytical calculations were performed in the framework of the classical long-range approximation. A model accounting the exchange effects in the range of small overlap of the electron shells of interacting molecules has been suggested to describe the dipole moment of the CH4-N2 van der Waals complexes in analytical form for large intermolecular separations including the range of potential wells. In this model the total dipole moment is considered to be the sum of exchange, induction and dispersion contributions.
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Steffen, Julien Verfasser], Bernd [Akademischer Betreuer] [Hartke e Carolin [Gutachter] König. "Towards High-Quality Black-Box Chemical Reaction Rates with System-Specific Potential Energy Surfaces / Julien Steffen ; Gutachter: Carolin König ; Betreuer: Bernd Hartke". Kiel : Universitätsbibliothek Kiel, 2020. http://nbn-resolving.de/urn:nbn:de:gbv:8-mods-2020-00061-7.
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Steffen, Julien [Verfasser], Bernd [Akademischer Betreuer] Hartke e Carolin [Gutachter] König. "Towards High-Quality Black-Box Chemical Reaction Rates with System-Specific Potential Energy Surfaces / Julien Steffen ; Gutachter: Carolin König ; Betreuer: Bernd Hartke". Kiel : Universitätsbibliothek Kiel, 2020. http://d-nb.info/1205735372/34.
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Belisario-Lara, Daniel E. "Pyrolysis of Jet Propellants and Oxidation of Polycyclic Aromatic Radicals with Molecular Oxygen: Theoretical Study of Potential Energy Surfaces, Mechanisms, and Kinetics". FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3819.
Testo completoAbstract (sommario):
Two reaction classes have been studied computationally including the pyrolysis of various components of airplane fuels, such as decane, dodecane, butylbenzene isomers, and JP-10 (exo-tetrahydrodicyclopentadiene), and oxidation of a group of molecules belonging to the class of Polycyclic Aromatic Hydrocarbons (PAHs). Investigation of both reaction classes have been performed using ab initio quantum chemistry methods with the Gaussian 09 and MOLPRO programs at various levels of theory. Initially, Potential Energy Surfaces (PES) were generated at the G3(MP2,CC)/B3LYP/6-311G** level of theory for various radicals involved in the reactions as reactants, intermediates, transition states, and products. The next step was to perform RiceRamsperger-Kassel-Marcus (RRKM) / Master Equation calculations in order to calculate rate constants and branching ratios of different products at various temperatures and pressures characteristic for combustion flames. All calculations were then compared with previous works on similar systems available in the literature. The results of these simulations along with previous data were then used to formulate guidelines for the pyrolysis and oxidation patterns of larger and more complex systems, in order to achieve a better understanding of the pathways to the end products in airplane jet engines.
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Okazaki, Susumu, e Atsushi Yamada. "A quantum equation of motion for chemical reaction systems on an adiabatic double-well potential surface in solution based on the framework of mixed quantum-classical molecular dynamics". AIP Publishing, 2008. http://hdl.handle.net/2237/20836.
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Henkelman, Graeme. "Methods for calculating rates of transitions with application to catalysis and crystal growth /". Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/8557.
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Ibargüen, becerra César. "Effet des forces de van der Waals sur la dynamique de l'azote et de l'hydrogène en interaction avec la surface de W(100)". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0261.
Testo completoAbstract (sommario):
Une littérature scientifique nourrie est consacrée aux processus élémentaires hétérogènes se produisant à l’interface gaz-solide en raison de leur rôle clé dans de nombreux domaines. Ainsi, l’interaction d’atomes et de molécules avec les surfaces revêt une importance primordiale dans l’étude de la catalyse hétérogène, la combustion, la corrosion, le stockage de l’hydrogène, l’industrie automobile et pétrolière, les interactions plasma/paroi dans le contexte du réacteur expérimental thermonucléaire (ITER), les technologies du spatial, la chimie atmosphérique et l’astrochimie, pour citer quelques exemples. Lorsqu'un atome ou une molécule entre en collision avec une surface, de nombreux processus élémentaires peuvent avoir lieu. Ils dépendent de nombreux facteurs tels que : l'énergie de collision du projectile, l'angle d'incidence sur la surface, la température de surface, l'état initial le des molécules, le transfert d'énergie entre la surface des projectiles, etc… Tous ces facteurs influencent fortement les mécanismes réactionnels et la dynamique de ces processus. Les expériences de faisceaux moléculaires permettent un contrôle toujours plus précis de l'état initial des réactifs associé à un caractérisation fine des produits de réactions. Cependant, dans la plupart des cas, ces observations expérimentales ne fournissent pas tous les détails qui nous permettent de décrire finement les mécanismes gouvernant les processus élémentaires étudiés. Par conséquent, l'élaboration de modèles théoriques devient essentielle pour en rationaliser la description. L'objectif principal de ce travail de thèse est de proposer une analyse de la dynamique de plusieurs processus élémentaires pouvant se produire sur une surface de W(100) en contact avec de l'hydrogène et de l'azote (diffusion inélastique de N2 et H2, l'adsorption dissociative et non dissociative de H2 et l'adsorption et l'absorption de H et N). Par rapport aux études antérieures, la nouveauté de ce travail réside dans la prise en compte des interactions à longue distance de type van der Waals, qui s’avèrent essentielles lorsqu'on souhaite atteindre un bon accord théorie expérience dans le régime des faibles énergies de collision. Les résultats sont comparés aux données expérimentales disponibles et aux résultats théoriques antérieurs. Des simulations de dynamique moléculaire quasi-classique sont réalisés à l'aide de surfaces d'énergie potentielle (PES) basées sur la théorie de la fonctionnelle de la densité, tenant compte d’interactions non locales, telles que les forces de van der Waals. La dissipation de l’énergie aux vibrations du réseau et aux excitations électroniques est prise en compte au moyen de modèles effectifsAn important part of scientific literature is devoted to the heterogeneous elementary processes occurring at gas-solid interface due to their great importance and key role in many different domains and applications. Thus, interaction of gas atoms/molecules with surface reactions are of primary importance in the study of: heterogeneous catalysis, combustion of solid fuel and coal gasification, processes of corrosion, hydrogen storage in solid material, automotive and oil industry, plasma-wall interactions in the context of thermonuclear experimental reactor (ITER), atmospheric re-entries technologies and astrochemistry, to name some examples. When an atom or molecule impinges on a surface many different elementary processes can take place, which depends on factors such as: the collision energy of the projectile, the angle of incidence to the surface, the surface temperature, the initial state of the molecules, the transference of energy projectiles-surface, etc. All these factors determines the mechanisms of reaction and the dynamics of the processes. Experimental molecular beams (MB) and other experimental techniques are able to accurately control the initial state of the reactive and characterizing products of gas-surface reactions. However, in most of the case experimental techniques do not provide enough details about the mechanisms through which elementary processes occur. Consequently, theoretical models becomes essential to rationalize the description that in certain cases the experiments do not reach.The main goal of this thesis work is to propose an analyze of the dynamics of several elementary processes occurring on a W(100) surface, such as: the inelastic scattering of N2 and H2, the dissociative and non-dissociative adsorption of of H2 and the adsorption and absorption of H and N. Compared to previous studies, the novelty of this work resides in the taking into account of van der Waals long-distance interactions, which are essential to reach a good agreement between theoretical and experiment results, especially at low collision energy regime. To rationalize the non-adiabatic effects, the energy dissipation to lattice vibrations and electronic excitation are taken in to account by means of GLO and LDFA models respectively
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Keller, Johannes Friedrich [Verfasser], Caroline [Akademischer Betreuer] Lasser, George A. [Akademischer Betreuer] Hagedorn e Christian [Akademischer Betreuer] Lubich. "Quantum Dynamics on Potential Energy Surfaces : Simpler States and Simpler Dynamics / Johannes Friedrich Keller. Betreuer: Caroline Lasser. Gutachter: Caroline Lasser ; George A. Hagedorn ; Christian Lubich". München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1078420599/34.
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Layfield, Joshua Parker. "Theoretical studies of the dynamics of gas-phase and gas/surface atom+alkane reactions and of the structure and dynamics of water confined between hydrophobic surfaces". Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/37222.
Testo completoAbstract (sommario):
Comprehension of reactive chemical dynamics in the gas phase and at the gas/organic-surface interface and non-reactive dynamics at the interface between hydrophobic surfaces and water requires an understanding of the fundamental atomic and molecular interactions that undergird these important phenomena. In an effort to study these regimes of chemical interaction, we have performed computational simulations that probe the dynamics of chemical systems that exemplify each of these domains. To study gas-phase chemical dynamics, we reparametrized semiempirical Hamiltonians so that they can accurately describe the potential energy surfaces for two distinct atom+alkane reactions. In addition to their demonstrated accuracy, these methods possess the attractive quality of being computationally inexpensive enough to afford extensive direct-dynamics trajectory studies. Our results on the dynamics of atom+alkane hydrogen-abstraction reactions have shown good agreement with experimental metrics that are as diverse as product velocity distributions, excitation functions, angular distributions and rovibrational state distributions for diatomic products of the abstraction. We have demonstrated that our reparametrized Hamiltonians are suitable for investigating gas-phase reactions with up to 15 (5 heavy) atoms and that they are appropriate for studying reactions beyond the gas phase, especially gas/surface reactions.
By employing our semiempirical methods within a quantum-mechanics/molecular-mechanics hybrid scheme we are able to examine hydrogen-abstraction reactions of fluorine atoms with alkanethiolate self-assembled monolayers. Our simulations reproduce the general trends of experimental results for the cousin F+squalane reaction. Our simulations also probe the role that secondary collisions play in determining the final internal and translational energy of the product HF molecules. For instance, we determined that very few interactions with the SAM surface were required to cool rotational and translational modes of the HF product, while its vibrational energy remains unchanged on the time scale that HF molecules trap on the SAM surface.
Moving beyond the gas/organic surface interface, we have also performed molecular-dynamics simulations of thin water films confined between hydrophobic SAM surfaces. These simulations illuminated the structural and dynamics behavior induced in the water films by confinement in hydrophobic environments. While most effects of the surface do not penetrate deep into the water layers we have noted that enhanced lateral diffusion of water molecules can persist in these films with > 1 nm length scales. We have elucidated a possible mechanistic precursor for the attractive forces seen in experimental measurement of the hydrophobic effect.Ph. D.
37
Kolmann, Stephen. "Accurate studies of weakly bound systems". Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/12895.
Testo completoAbstract (sommario):
This thesis investigates the “grand challenge” problem of hydrogen storage. We use H2 binding to Li+-doped benzene as a model for Li-doped metal-organic framework (MOF) and Li-doped carbon-based hydrogen storage materials. The lithium dopant acts to increase the H2 binding enthalpy, with the hope that these materials may be appropriate for room temperature hydrogen storage. Improvements to the iterative procedure used to Grow modified Shepard interpolated PESs are developed in the context of the SSSH radical, a “floppy” system where the ground state structure has not previously been characterised. These improvements allow us to determine that the H atom in SSSH is localised on one side of the SSS plane, despite the SSSH zero-point energy being significantly greater than the SSSH torsional barrier. The redundant coordinates used in the modified Shepard interpolation are examined in the context of a particularly pathological weakly bound system, the protonated water dimer, H5O2+. This investigation allows us to determine appropriate coordinates for H5O2+, which although accurate, are cumbersome to apply. We develop a simple, pragmatic solution that may be easily applied to other weakly bound systems. These improvements to the Grow methodology enable us to develop an accurate modified Shepard interpolation for the H2-Li+-benzene PES. Quantum and anharmonic effects are studied in H2-Li+-benzene using quantum diffusion Monte Carlo (QDMC) and path integral Monte Carlo (PIMC) simulations. These simulations allow the internal energy of the system to be calculated and, together with the ideal gas approximation, allow enthalpy to be determined. The results of the QDMC and PIMC simulations on H2-Li+-benzene show that accurate estimations of Hbind cannot be obtained from the electronic energy alone. They also highlight the importance of anharmonicity in weakly bound systems.
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Ramachandran, Ragav. "Excitation collisionnelle des molécules NH et ND par He et H2 : théorie, comparaison avec les expériences et application astrophysique". Thesis, Normandie, 2020. http://www.theses.fr/2020NORMLH02.
Testo completoAbstract (sommario):
La molécule NH est cruciale dans la chimie de l'azote interstellaire car elle est un intermédiaire lors de la formation d'ammoniac dans l'MIS. L'abondance de cette espèce est une sonde cruciale de la chimie de l'azote. Avec les progrès des techniques d'observation, des transitions hautement résolues de ces molécules dans l'MIS ont été observées. Cependant, les rapports d'abondance observés des hydrures d'azote ne correspondent pas aux modèles astrochimiques. Les isotopologues sont utilisés pour sonder les voies chimiques. Pour une analyse précise de ces observations spectrales, des méthodes de modélisation non-LTE sont utilisées qui nécessitent des coefficients de taux de collision NH et ND précis. Dans ce travail, nous présentons des coefficients de taux résolus fins et hyperfins pour la (dé-)excitation de NH/ND due aux collisions avec He et celle de NH avec H2 qui devraient permettre une détermination précise de l'abondance de NH à partir des spectres d'observation. Dans cette thèse, nous présentons des PES ab initio hautement corrélés des NH-He et NH-H2 complexes Van der Waals. Les calculs des coefficients de taux état-à-état résolus fins et hyperfins pour les collisions NH-He ont été effectués en utilisant le nouveau PES pour les températures jusqu'à 350 K et les collisions ND-He pour les températures jusqu'à 200 K. De la comparaison, nous observons qu'il y a une différence significative entre les coefficients de taux actuels et précédents, qui est attribuée essentiellement à l'inclusion de l'effet vibrationnel dans les nouveaux calculs et à la comparaison entre les résultats NH-He et ND-He montre l'importance de calculer explicitement les coefficients de taux ND-He. Nous présentons également les premiers calculs pour NH-H2. Étant donné que les coefficients de taux He et H2 diffèrent considérablement, les ensembles de données collisionnelles NH-He et NH-H2 devraient être utilisés pour réviser l'abondance de NH dans l'espaceNH molecule plays a crucial role in the interstellar nitrogen chemistry as it acts as an intermediate during the formation of the ubiquitous ammonia. Abundance of this species is a crucial probe of the nitrogen chemistry. With the advancements in the observational techniques, highly resolved transitions of these molecules in the ISM have been observed. However, the observed abundance ratios of nitrogen hydrides do not match with astrochemical models. The isotopologues are used to probe chemical pathways. For accurate analysis of these spectral observations, non-LTE modeling methods are employed which requires accurate NH and ND collisional rate coefficients. In this work, we present fine and hyperfine resolved rate coefficients for the (de-)excitation of NH/ND due to collisions with He and that of NH with H2 that should allow accurate determination of the NH abundance from the observational spectra. In this thesis we present highly correlated ab initio PESs of the NH-He and NH-H2 Van der Waals complexes. Calculations of fine and hyperfine resolved state-to-state rate coefficients for NH-He collisions were performed using the new PES for temperatures up to 350 K and ND-He collisions for temperatures upto 200 K. From the comparison, we observe that there is a significant difference between the present and previous rate coefficients, which is attributed essentially to the inclusion of vibrational effect in the new calculations and comparison between NH-He & ND-He results shows the importance of calculating ND-He rate coefficients explicitly. We also present the first calculations for NH-H2. As the He and H2 rate coefficients differ significantly, both the NH-He and NH-H2 sets of collisional data should be used to revise the NH abundance in space
39
Opoku-Agyeman, Bernice. "Complexities in Nonadiabatic Dynamics of Small Molecular Anions". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503094708588515.
Testo completo
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Schröder, Benjamin. "Theoretical high-resolution spectroscopy for reactive molecules in astrochemistry and combustion processes". Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://hdl.handle.net/21.11130/00-1735-0000-0005-12DA-1.
Testo completo
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Martin, Ludovic. "Contribution théorique à l'étude de la réactivité élémentaire gaz/surface d'intérêt en rentrée atmosphérique". Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13823/document.
Testo completoAbstract (sommario):
Lors d’une rentrée atmosphérique, les boucliers thermiques des véhicules spatiaux subissent un échauffement considérable dont une fraction significative (~30%) est attribuée aux réactions chimiques à leur surface. Cette thèse contribue à la compréhension de cette réactivité hétérogène, la catalycité, au moyen des outils de la chimie théorique. Une méthode de construction de surface d’énergie potentielle globale est développée et appliquée à l’étude de la dynamique de processus élémentaires (adsorption moléculaire dissociative, absorption atomique, recombinaison Eley-Rideal …) pour les systèmes chimiques N,N2/W(100,110) et O,O2/Cu(100). Ces approches sont ensuite couplées à un modèle cinétique permettant de quantifier la catalycitéDuring an atmospheric re-entry, the thermal shields of spacecrafts undergo an important heating, a significant fraction (~30%) of which is due to the chemical reactions at their surface. This thesis is a contribution to the understanding of this heterogeneous reactivity, catalycity, with the tools of theoretical chemistry. A method to build a global potential energy surface is developed and applied to the study of elementary processes dynamics (dissociative molecular adsorption, atomic absorption, Eley-Rideal recombination …) for the N,N2/W(100,110) and O,O2/Cu(100) chemical systems. These approaches are then coupled with a kinetic model quantifying catalycity
42
Lara, Moreno Miguel. "Etude des mécanismes possibles de formation et de destruction d'anions dans le milieu interstellaire". Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0220/document.
Testo completoAbstract (sommario):
L’étude des mécanismes de formation et de destruction des anions moléculaires est devenu un champ d’intérêt prononcé après la détection récente de six anions moléculaires (C4H-, C6H-, C8H-, CN-, C3N-, C5N-) dans le milieu interstellaire.Dans les environnements interstellaires où la densité d’électrons est relativement importante, le canal principal de formation de ces anions devrait être l’attachement électronique radiatif. Mais il manque aujourd’hui des données expérimentales et théoriques permettant d’évaluer cette hypothèse. D’autre part, le photodétachement est la principale cause de destruction de ces anions dans les nuages diffus et les régions de photodissociation. Une approche basée sur un développement monocentrique est appliquée à l’étude de ces deux processus opposés que sont le photodétachement et l’attachement électronique radiatif. Les résultats obtenus avec la présente méthode sont comparés à des données expérimentales et théoriques précédemment rapportées et montrent un bon accord. Cette méthode est ensuite utilisée pour déterminer les constantes de vitesse nécessaires pour confirmer si ces mécanismes sont cruciaux pour la chimie d’anions interstellaires. En plus des constantes de vitesse de formation et de destruction des anions, les constantes de vitesse d’excitation collisionnelle sont nécessaires pour modéliser les abondances observées des anions. Nous avons choisi de porter notre effort sur le calcul des constantes de vitesse de transition entre états rotationels de la molécule C3N- dans son état vibrationnel fondamental lors des collisions avec H2 et He en utilisant de nouvelles surfaces d’énergie potentiellesThe mechanisms of formation and destruction of molecular anions have become a field of special interest after the recent detection of six molecular anions (C4H-,C6H-, C8H-, CN-, C3N-, C5N-) in the interstellar medium. The main channel of formation of these anions is expected to be radiative electron attachment in environments where the density of electron is relatively important. There is however at themoment a lack of experimental and theoretical data allowing to assess this hypothesis. Photodetachment, on the other hand, is the main source of destruction of the anions in diffuse clouds and photodissociation regions. A single center expansion approach is applied to the study of both processes: photodetachment and radiative electron attachment. The results obtained with the present method are compared to previously reported experimental and theoretical data and show a good agreement.This method is then employed to determine the rate constants which are needed to confirm whether or not these mechanisms are crucial for the chemistry of the interstellar anions. Along with the formation and destruction rates, rotational excitation rate coefficients are needed to accurately model the observed anions abundances.We focus on the calculation of state-to-state rotational transitions rate coefficients of the C3N- molecule in its ground vibrational state in collisions with H2 and He using new potential energy surfaces
43
Bocklitz, Sebastian. "Conformational spectroscopy of flexible chain molecules near the folding limit". Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://hdl.handle.net/11858/00-1735-0000-002E-E35F-A.
Testo completo
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Cornaton, Yann. "Etude quantique des liaisons fortes et faibles : développement de fonctionnelles "doubles-hybrides" et de surfaces de potentiel analytiques". Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-00997412.
Testo completoAbstract (sommario):
Les travaux réalisés au cours de cette thèse se décomposent en deux thèmes principaux, eux-même subdivisés enplusieurs projets. D'une part, des travaux ont été menés concernant l'analyse et le développement de fonctionnelles " doubles hybrides ". Une analyse des fonctionnelles " doubles hybrides " à séparation linéaire le long de la connexionadiabatique a été proposée. Une nouvelle fonctionnelle " double hybride " à séparation de portée basée sur uneséparation alternative de l'énergie d'échange et de corrélation, RSDHf, a été développée. D'autre part, des travaux quant au développement de surfaces d'énergie potentielle (SEP) analytiques ont été menés. Un nouveau potentiel analytique a été proposé pour la description de la SEP des systèmes triatomiques. La combinaison de ce potentiel avec un potentiel électrostatique a été utilisé pour le développement de SEP analytiques pour de petits systèmes en interaction faible : H2O***HF, HF2-, Ne***ClF.
45
Toliautas, Stepas. "Elektroninio sužadinimo procesai fotoaktyviose organinėse molekulėse". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20140929_100514-01959.
Testo completoAbstract (sommario):
Elektroninio sužadinimo evoliucija šviesai jautriose molekulėse yra reiškinys, kuriuo remiantis įmanoma nagrinėti daugelį natūralių ir dirbtinių procesų: augalų ir bakterijų fotosintezę, regos mechanizmą, optomechaninių bei optoelektroninių prietaisų (pavyzdžiui, organinių šviestukų) veikimą. Teoriškai šis reiškinys modeliuojamas sprendžiant laikinę Šriodingerio lygtį. Deja, toks sprendimas realiems, praktiškai panaudojamiems junginiams šiandien yra per sudėtingas uždavinys, todėl jį tenka keisti supaprastinant nagrinėjamų junginių modelius arba sprendimo metodiką. Šioje disertacijoje aprašomų tyrimų tikslas buvo elektroninės struktūros skaičiavimų metodais (t. y. sprendžiant paprastesnę nuostoviąją Šriodingerio lygtį) ištirti elektroninio sužadinimo sukeltus procesus fotoaktyviose molekulėse ir sudaryti sužadinimo relaksaciją apibūdinančius potencinės energijos paviršių modelius. Parodoma, jog ta pačia metodika atliekamų tyrimų rezultatai paaiškina įvairiuose junginiuose vykstančius reiškinius: bakteriorodopsino baltymo funkcinės grupės vykdomą protono pernašą poliniame tirpiklyje, indolo-benzoksazino junginio optomechaninį ciklą, našią fosforescenciją organiniame silicio polimere bei šviestukams naudojamo metaloorganinio komplekso su prijungtomis krūvininkų pernašos grupėmis ypatybes.Evolution of the electronic excitation is a general process that can be used to explain many natural and artificial phenomena, such as photosynthesis in plants and bacteria, biological mechanism of vision, and operating principles of optomechanical and optoelectronic devices. This process is theoretically modeled by solving the time-dependent Schroedinger equation. However, such treatment is too computationally expensive to be used for practical molecular systems. Therefore, either models of the structure of the systems or the solving procedure itself must be simplified to get the desired results. The main goal of the research presented in this dissertation was to study processes caused by the electronic excitation in photoactive molecules using computational methods of electronic structure (i. e. solving the simpler time-independent Schroedinger equation) and to construct the potential energy surface models describing the energy relaxation in the investigated molecules. It is shown that the results of different investigations performed using the same procedure provide explanations of different phenomena in various compounds, such as: proton transfer in polar solvent, performed by a functional group of the bacteriorhodopsin protein; optomechanical cycle of the indolo-benzoxazine compound; efficient phosphorescence of the silicon-based organic polymer; and optical properties of organometallic emitter compound with additional charge-carrier groups.
46
Toliautas, Stepas. "Electronic excitation processes of photoactive organic molecules". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20140929_100526-37294.
Testo completoAbstract (sommario):
Evolution of the electronic excitation is a general process that can be used to explain many natural and artificial phenomena, such as photosynthesis in plants and bacteria, biological mechanism of vision, and operating principles of optomechanical and optoelectronic devices. This process is theoretically modeled by solving the time-dependent Schroedinger equation. However, such treatment is too computationally expensive to be used for practical molecular systems. Therefore, either models of the structure of the systems or the solving procedure itself must be simplified to get the desired results. The main goal of the research presented in this dissertation was to study processes caused by the electronic excitation in photoactive molecules using computational methods of electronic structure (i. e. solving the simpler time-independent Schroedinger equation) and to construct the potential energy surface models describing the energy relaxation in the investigated molecules. It is shown that the results of different investigations performed using the same procedure provide explanations of different phenomena in various compounds, such as: proton transfer in polar solvent, performed by a functional group of the bacteriorhodopsin protein; optomechanical cycle of the indolo-benzoxazine compound; efficient phosphorescence of the silicon-based organic polymer; and optical properties of organometallic emitter compound with additional charge-carrier groups.Elektroninio sužadinimo evoliucija šviesai jautriose molekulėse yra reiškinys, kuriuo remiantis įmanoma nagrinėti daugelį natūralių ir dirbtinių procesų: augalų ir bakterijų fotosintezę, regos mechanizmą, optomechaninių bei optoelektroninių prietaisų (pavyzdžiui, organinių šviestukų) veikimą. Teoriškai šis reiškinys modeliuojamas sprendžiant laikinę Šriodingerio lygtį. Deja, toks sprendimas realiems, praktiškai panaudojamiems junginiams šiandien yra per sudėtingas uždavinys, todėl jį tenka keisti supaprastinant nagrinėjamų junginių modelius arba sprendimo metodiką. Šioje disertacijoje aprašomų tyrimų tikslas buvo elektroninės struktūros skaičiavimų metodais (t. y. sprendžiant paprastesnę nuostoviąją Šriodingerio lygtį) ištirti elektroninio sužadinimo sukeltus procesus fotoaktyviose molekulėse ir sudaryti sužadinimo relaksaciją apibūdinančius potencinės energijos paviršių modelius. Parodoma, jog ta pačia metodika atliekamų tyrimų rezultatai paaiškina įvairiuose junginiuose vykstančius reiškinius: bakteriorodopsino baltymo funkcinės grupės vykdomą protono pernašą poliniame tirpiklyje, indolo-benzoksazino junginio optomechaninį ciklą, našią fosforescenciją organiniame silicio polimere bei šviestukams naudojamo metaloorganinio komplekso su prijungtomis krūvininkų pernašos grupėmis ypatybes.
47
Ringer, Ashley L. "From small to big". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28089.
Testo completoAbstract (sommario):
Thesis (M. S.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.Committee Chair: Sherrill, C. David; Committee Member: Bredas, Jean-Luc; Committee Member: El-Sayed, Mostafa A.; Committee Member: Harvey, Stephen C; Committee Member: Hernandez, Rigoberto.
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Gannouni, Mohamed Achref. "Approche théorique des collisions réactives de type ion-molécule". Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1108/document.
Testo completoAbstract (sommario):
La collision entre l'ion hydroxyle (OH+) et l'atome d'hydrogène (H) joue un rôle majeur en physico-chimie de l'atmosphère et en astrophysique. Pour l'étude de ce système, nous avons générés la surface d'énergie potentielle tridimensionnelle (SEP-3D) globale doublet de la réaction H + OH+ --- H2O+ (X2B1)--- O + H2+. Les calculs électroniques ont été effectués au niveau MRCI avec la base aug-cc-pV5Z en incluant la correction des erreurs de superposition de base (BSSE). Cette SEP couvre la région moléculaire et les régions des longues portées pour les différents canaux : OH+ + H, O + H2+ et la réaction d'échange d'hydrogène. La qualité de la SEP a été validée après une comparaison des constantes spectroscopiques de H2O+ (X2B1) et des fragments diatomiques, des niveaux rovibroniques de H2O+ (X2B1), l'énergie de dissociation et de la barrière à linéarité pour H2O+ (X2B1) aux données expérimentales et théoriques existantes. Un bon accord est trouvé. Après avoir déterminé la SEP, nous avons utilisé les outils de la dynamique quantique indépendante du temps pour calculer les sections efficaces élastiques et inélastiques désexcitation de OH+ (v=0, j=1, 2, 3, 4, 5, 6 et 7) en collision avec l'atome d'hydrogène sur un large domaine d'énergie cinétique. Nous avons ainsi déterminé les taux désexcitation rotationnelle pour des températures allant de 10 à 200K. Nous avons également utilisé la surface quadruplet de Martinez et al. pour déduire ces taux désexcitation. Les résultats montrent que les sections efficaces inélastiques calculées sur la surface doublet sont en moyenne au moins deux à trois fois plus importantes que leurs correspondantes obtenues sur la surface quartet. Les potentiels à longue portée des deux surfaces étant identiques, ce résultat montre qu'un modèle basé sur la seule longue portée du potentiel ne pourrait pas rendre compte de la dynamique inélastique de ce systèmeThe collision between the hydroxyl cation (OH+) and hydrogen atoms (H) plays a major role in physical chemistry of the atmosphere and astrophysics. To study this system, we generated the global three-dimensional potential energy surface (3D-PES) of the reaction H + OH+ ---- H2O+ (X2B1) ---- O + H2+. The electronic calculations were performed at the MRCI level with aug-cc-pV5Z basis including the basis set superposition error (BSSE) correction. This PES covers the molecular region and the long ranges close to the OH+ + H, O + H2+ and the hydrogen exchange channels. The quality of the PES is checked after comparison of the spectroscopic constants of H2O+ (X2B1) and of the diatomic fragments, the rovibronic levels, the dissociation energy, and the barrier to linearity of H2O+ (X2B1) to available experimental and theoretical data. A good agreement is found. Then, we used the tools of time-independent Quantum Dynamics to calculate the elastic and inelastic cross sections for the de-excitation of OH+ in collision with the hydrogen atom over a wide range of kinetic energy. We have thus determined the rotational de-excitation rate coefficients for temperatures ranging from 10 up to 200K. The results show that the inelastic cross sections on the doublet surface are on average at least two to three times larger than their cross section obtained on the previously computed cross sections using the quartet surface. Since, the long range parts of the doublet and the quartet PESs are identical, our work invalidates hence previous cross section determination. When only long range potentials are considered. Therefore, we recommend using fully the global 3D PES for scattering and reactive collision relevant for atmospheric and astrophysical studies
49
Mačernis, Mindaugas. "Aplinkos poveikis fotoindukuotiems reiškiniams organinėse molekulėse". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20110307_144829-49678.
Testo completoAbstract (sommario):
Disertacijoje nagrinėjamas galimas aplinkos poveikis organinių molekulių elektroninių būsenų savybėms. Tam tikslui yra naudojami kompiuterizuotieji kvantinės mechanikos metodai, kuriais remiantis nagrinėjamos įvairių molekulių savybės. Ištirtos 2-(N-metil-α-iminoethyl)-fenol ir N-triphenylmethylsalicylidene imine molekelulių, esančių poliniame tirpiklyje, struktūros pagrindinėje ir sužadintose elektroninėse būsenose. Pirmą kartą parodyta, kad, norint gauti teisingą kokybinį ir artimą kiekybiniam vidujmolekulinės protono pernašos potencinės energijos paviršių, būtina atsižvelgti į polinių tirpiklio molekulių kuriamą vandenilinių ryšių tinklą bei į nulinių svyravimų energijas. Pastarieji ir nulemia protono pernašos vyksmo kryptį bei efektyvumą. Parodyta, kad anilų klasės molekulių konformerų susiformavimas priklauso nuo tirpiklio poliškumo, o jų susidarymas savo ruožtu konkuruoja su klasterių iš tirpiklio molekulių susiformavimo galimybėmis.
Pirmą kartą parodyta, kad dipolinio momento vertė bakteriorodopsine yra nulemta membranos paviršiuose esančių radikalų.
Pademonstruota, kad stilbazolio molekulė deformuojasi ir sudaro naujus konformerus (pademonstruota dviejų formų atsiradimo galimybė) tik esant molekulėms tirpalo apsuptyje. Šis rezultatas paaiškino eksperimente stebimus skirtuminių spektrinių pokyčių evoliucijos prigimtį.
Apskaičiuotos ir išanalizuotos karotinoidų - luteino, violaksantino ir zeaksantino molekulių - žemiausios sužadintos elektroninės būsenos. Parodyta... [toliau žr. visą tekstą]To explore changes caused by the environment on the internal characteristics of an organic molecule is the objective of the thesis. For this purpose we investigate a variety of organic molecules. Using various methods of quantum mechanics calculations possible influence of a polar solvent on the ground and excited states of 2-(N-metil-α-iminoethyl)-fenol and N-triphenylmethylsalicylidene imine is considered. It is shown for the first time that in order to obtain the correct qualitative and quantitative interpretation of possible pathways of the intermolecular proton transfer the hydrogen network of the polar solvent molecules together with the zero point energy have to be taken into consideration. It is also shown that conformational variability of anil-type molecules in polar solvents is competing with clusters formation of solvent molecules. It is shown for the first time that the dipole moment of bacteriorhodopsin is mainly defined by cytoplasmic and extracellular coils on the surfaces of the membrane. It is also demonstrated that the stilbazole molecule experiences the deformation resulting in formation of new conformers (at least two forms are present) in the solvent surrounding. The experimental data of the transient spectroscopy were explained in the basis of these model calculations. The lowest excited states of carotinoids, such as lutein, zeaxanthin and violoxantin are calculated and analyzed. Sensitivity of the excited electronic state on the polar environment is... [to full text]
50
Aoto, Yuri Alexandre. "Construção da superfície de energia potencial global para o sistema [H,S,F]". Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-22102013-083700/.
Testo completoAbstract (sommario):
Este projeto tem dois objetivos. Primeiramente estudou-se a aplicabilidade dos splines tricúbicos para a construção de superfícies de energia potencial globais. Um dos obstáculos que este método tem de superar e a escolha de um sistema de coordenadas apropriado, que minimize a influência de pontos não físicos. Para isto, propôs-se o uso do sistema de coordenadas de Pekeris, nunca usado para este fim. Este procedimento foi realizado para três sistemas químicos bem descritos na literatura, [Cl,H2], [F,H,D] e [H,O,Cl], cujas superfícies de energia potencial e propriedades das reações foram usadas como referência. Com base nestes modelos, aplicamos o método proposto variando-se a quantidade e a disposição dos nós das interpolações, a fim de verificar sua influência na qualidade das superfícies interpoladas. Os resultados mostram que as superfícies construídas por este método reproduzem muito bem os cálculos de dinâmica química, tanto por métodos quânticos quanto por métodos clássicos. Para isto, os nós da interpolação devem cobrir as regiões mais importantes da superfície de energia potencial e os valores mais baixos das coordenadas de Pekeris devem ser priorizados. O segundo objetivo consiste na aplicação deste procedimento na construção da superfície de energia potencial [H,S,F]. Com esta superfície, diversas características deste sistema foram analisadas, tais como geometrias dos pontos estacionários, energias relativas e frequências vibracionais. Os valores obtidos estão de acordo com os dados descritos na literatura. A superfície construída também foi usada para a realização de cálculos de dinâmica para a reação F+HS → S+FH. Observamos a existência de dois tipos de mecanismos, um com a formação de um intermediário de longa duração e outro com a abstração direta do átomo de hidrogênio.This project has two goals. First, we studied the applicability of the tricubic splines to construct global potential energy surfaces. One of the diculties this approach has to overcome is the choice of an appropriate coordinate system that minimises the in uence of non-physical points. For such, we proposed the use of the Pekeris coordinate system, never employed for this purpose. This procedure was carried out for three well described systems, [Cl,H2], [F,H,D] and [H,O,Cl], whose potential energy surfaces and reaction properties were taken as references. Based on these models, we applied the proposed method varying the amount and arrangement of the interpolation knots, to verify their influence on the quality of the interpolated surfaces. The results showed that surfaces constructed by this approach reproduce very well the chemical dynamics calculations, both for the quantum as well as for the classical methods, provided that the interpolation knots cover the most important regions of the potential energy surfaces, and the lower values of the Pekeris coordinates are prioritised. The second goal was the application of this procedure to the construction of the [H,S,F] potential energy surface. With this surface, several characteristics of this system were analysed, such as the geometry of the stationary points, relative energies and vibrational frequencies. The values obtained are in agreement with the data described in the literature. The constructed surface was also used for quantum dynamics calculations on the reaction F + HS → S + FH. We observed two kinds of mechanisms, one of them with the formation of a long-living intermediate and the other with the direct abstraction of the hydrogen atom.