Log in

Relevant bibliographies by topics / CPMD / Journal articles

To see the other types of publications on this topic, follow the link: CPMD.

Journal articles on the topic 'CPMD'

Author: Grafiati

Published: 4 June 2021

Last updated: 6 September 2023

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the top 50 journal articles for your research on the topic 'CPMD.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.

1

Putra, Achmad Noerkhaerin, Unah Indayah, Nokiyah Nokiyah, and Mas Bayu Syamsunarno. "Improving quality of cassava peel meal as raw material for tilapia feed." Depik 11, no. 3 (October 1, 2022): 319–26. http://dx.doi.org/10.13170/depik.11.3.24620.

Full text

Abstract:

Cassava peel meal (CPM) has potential as a raw material for fish feed due to its abundant availability and good nutritional content. The high crude fiber content inhibits the use of CPM as a raw material for fish feed. Therefore, this study aims to evaluate the effect of Aspergillus niger fermentation of CPM on dietary nutrient digestibility and growth performance of tilapia (Oreochromis niloticus). It was conducted in 2 stages. The first stage was a fermentation process of CPM, which used a factorial randomized design consisting of a dose difference of A. niger, namely 10, 15, 20, 30 g.kg-1 and a fermentation time of 0, 12, 24 hours with 3 replications each. At a dose of 1.5% of A. niger during 24 hours of fermentation, the crude fiber content of fermented CPM was reduced up to 7.19%. the second stage was a 45 days feeding trial on tilapia used a completely randomized design consisting of 3 different treatments with 3 replications, namely: reference feed, unfermented cassava peal meal based diet (CPMD), and A. niger fermented CPMD. A. niger fermented CPMD showed an increase in growth, dry matter, protein, energy, and raw material digestibility, as well as daily growth rate compared to unfermented CPMD. The daily growth rate of fermented CPMD of 1.32%/day was significantly higher with P0.05 than the unfermented CPMD of 0.72%/day. Furthermore, the digestibility value of material test in the fermented CPMD (48.73%) was significantly higher (P0.05) than unfermented CPMD (11.74%). These results indicate that A. niger fermented CPM has the potential to be used as raw material for tilapia fish feed. Keywords:Aspergillus nigerFermentationTilapiaCrude fiber

APA, Harvard, Vancouver, ISO, and other styles

2

Huang, Qingxiang, and Jian Cao. "Research on Coal Pillar Malposition Distance Based on Coupling Control of Three-Field in Shallow Buried Closely Spaced Multi-Seam Mining, China." Energies 12, no. 3 (January 31, 2019): 462. http://dx.doi.org/10.3390/en12030462.

Full text

Abstract:

In order to explore the rational coal pillar malposition distance (CPMD) based on coupling control of stress field, displacement field and fracture field (three-field) in shallow buried closely spaced multi-seam (SBCSM-S) mining, and realize coupling control of underground concentrated stress and ground surface fractures, taking the No. 1–2 and No. 2–2 coal seams mining in the northward east area of Ningtiaota coal mine as background, through physical simulation and theoretical analysis, the three-field evolution in SBCSM-S mining was analysed, the effect of different CPMD on coal pillar concentrated stress, ground surface subsidence and fractures development was revealed, and the rational CPMD based on coupling control of three-field was put forward. The results show that the concentrated fractures and concentrated stress are due to the strata’s uneven subsidence by coal pillars. Rational arrangement of CPMD can avoid the superposition of vertical stress caused by upper and lower coal pillars and reduce the development of ground fractures and uneven subsidence. Two theoretical models were established: one was based on the control of a concentrated stress field, the other on the control of the displacement and fracture fields. These results will be applied in a follow-up arrangement at the Ningtiaota coal mine, and can provide a new way for safe and green mining in SBCSM-S.

APA, Harvard, Vancouver, ISO, and other styles

3

Lemke, Kono H. "Structure and solvation dynamics of the hydroxide ion in ice-like water clusters: a CCSD(T) and car–parrinello molecular dynamics study." Physical Chemistry Chemical Physics 23, no. 34 (2021): 18990–98. http://dx.doi.org/10.1039/d1cp02524d.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Mosconi, Edoardo, Claudio Quarti, Tanja Ivanovska, Giampiero Ruani, and Filippo De Angelis. "Structural and electronic properties of organo-halide lead perovskites: a combined IR-spectroscopy and ab initio molecular dynamics investigation." Phys. Chem. Chem. Phys. 16, no. 30 (2014): 16137–44. http://dx.doi.org/10.1039/c4cp00569d.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Frank, Irmgard. "Some simple facts about water: CPMD simulation." Molecular Physics 118, no. 21-22 (August 6, 2020): e1802074. http://dx.doi.org/10.1080/00268976.2020.1802074.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Nelissen, Geoffrey, Konstantinos Bletsas, and Joël Goossens. "CPMD-mindful task assignment for NPS-F." Real-Time Systems 50, no. 5-6 (July 19, 2014): 585–91. http://dx.doi.org/10.1007/s11241-014-9206-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Tilocca, Antonio, and Alastair N. Cormack. "The initial stages of bioglass dissolution: a Car–Parrinello molecular-dynamics study of the glass–water interface." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 467, no. 2131 (February 9, 2011): 2102–11. http://dx.doi.org/10.1098/rspa.2010.0519.

Full text

Abstract:

The initial dissolution stages following implantation of a biomaterial in a physiological environment are critical for its bioactive properties. Car–Parrinello molecular-dynamics (CPMD) simulations of the interface between the 45S5 bioglass surface and liquid water have been carried out to investigate these processes. The analysis of a 40 ps CPMD trajectory has highlighted the potential mechanism of Na + /H + exchange, leading to formation of surface silanols through water dissociation. Moreover, by comparing the properties of water layers arranged at different distances from the glass surface, we discuss the way in which the particular structure and composition of the bioglass surface affects the hydrogen-bond network and orientation of water in its close proximity.

APA, Harvard, Vancouver, ISO, and other styles

8

Bühl, Michael. "Structure and stability of aquotetrafluorouranyl(VI) in the solid state — Density functional study of [UO2F4(H2O)][NMe4]2·2H2O,." Canadian Journal of Chemistry 87, no. 7 (July 2009): 818–23. http://dx.doi.org/10.1139/v08-182.

Full text

Abstract:

Periodic density functional computations have been performed for solid [UO2F4(H2O)][NMe4]2·2H2O at the BLYP level. A model with disordered fluoro and aquo ligands in the uranyl anion is significantly lower in energy than one with a symmetrical assignment of these sites, which was favored in the original X-ray crystallography study. According to optimized energies and Car–Parrinello molecular dynamics (CPMD) simulations, the [UO2F4(H2O)]2− ion in the solid is stable with respect to loss of the coordinated water molecule. In contrast, CPMD simulations had found this ligand to be unbound in aqueous solution. The role of the counterions in stabilizing the higher coordination number in the crystal is discussed.

APA, Harvard, Vancouver, ISO, and other styles

9

Yu, Shi, Ruizhi Chu, Xiao Li, Guoguang Wu, and Xianliang Meng. "Combined ReaxFF and Ab Initio MD Simulations of Brown Coal Oxidation and Coal–Water Interactions." Entropy 24, no. 1 (December 31, 2021): 71. http://dx.doi.org/10.3390/e24010071.

Full text

Abstract:

In this manuscript, we use a combination of Car–Parrinello molecular dynamics (CPMD) and ReaxFF reactive molecular dynamics (ReaxFF-MD) simulations to study the brown coal–water interactions and coal oxidation. Our Car–Parrinello molecular dynamics simulation results reveal that hydrogen bonds dominate the water adsorption process, and oxygen-containing functional groups such as carboxyl play an important role in the interaction between brown coal and water. The discrepancy in hydrogen bonds formation between our simulation results by ab initio molecular dynamics (CPMD) and that by ReaxFF-MD indicates that the ReaxFF force field is not capable of accurately describing the diffusive behaviors of water on lignite at low temperatures. The oxidations of brown coal for both fuel rich and fuel lean conditions at various temperatures were investigated using ReaxFF-MD simulations through which the generation rates of major products were obtained. In addition, it was observed that the density decrease significantly enhances the generation of gaseous products due to the entropy gain by reducing system density. Although the ReaxFF-MD simulation of complete coal combustion process is limited to high temperatures, the combined CPMD and ReaxFF-MD simulations allow us to examine the correlation between water adsorption on brown coal and the initial stage of coal oxidation.

APA, Harvard, Vancouver, ISO, and other styles

10

Jezierska, Aneta, Kacper Błaziak, Sebastian Klahm, Arne Lüchow, and Jarosław J. Panek. "Non-Covalent Forces in Naphthazarin—Cooperativity or Competition in the Light of Theoretical Approaches." International Journal of Molecular Sciences 22, no. 15 (July 27, 2021): 8033. http://dx.doi.org/10.3390/ijms22158033.

Full text

Abstract:

Non-covalent interactions responsible for molecular features and self-assembly in Naphthazarin C polymorph were investigated on the basis of diverse theoretical approaches: Density Functional Theory (DFT), Diffusion Quantum Monte Carlo (DQMC), Symmetry-Adapted Perturbation Theory (SAPT) and Car-Parrinello Molecular Dynamics (CPMD). The proton reaction paths in the intramolecular hydrogen bridges were studied. Two potential energy minima were found indicating that the proton transfer phenomena occur in the electronic ground state. Diffusion Quantum Monte Carlo (DQMC) and other levels of theory including Coupled Cluster (CC) employment enabled an accurate inspection of Potential Energy Surface (PES) and revealed the energy barrier for the proton transfer. The structure and reactivity evolution associated with the proton transfer were investigated using Harmonic Oscillator Model of Aromaticity - HOMA index, Fukui functions and Atoms In Molecules (AIM) theory. The energy partitioning in the studied dimers was carried out based on Symmetry-Adapted Perturbation Theory (SAPT) indicating that dispersive forces are dominant in the structure stabilization. The CPMD simulations were performed at 60 K and 300 K in vacuo and in the crystalline phase. The temperature influence on the bridged protons dynamics was studied and showed that the proton transfer phenomena were not observed at 60 K, but the frequent events were noticed at 300 K in both studied phases. The spectroscopic signatures derived from the CPMD were computed using Fourier transformation of autocorrelation function of atomic velocity for the whole molecule and bridged protons. The computed gas-phase IR spectra showed two regions with OH absorption that covers frequencies from 2500 cm−1 to 2800 cm−1 at 60 K and from 2350 cm−1 to 3250 cm−1 at 300 K for both bridged protons. In comparison, the solid state computed IR spectra revealed the environmental influence on the vibrational features. For each of them absorption regions were found between 2700–3100 cm−1 and 2400–2850 cm−1 at 60 K and 2300–3300 cm−1 and 2300–3200 cm−1 at 300 K respectively. Therefore, the CPMD study results indicated that there is a cooperation of intramolecular hydrogen bonds in Naphthazarin molecule.

APA, Harvard, Vancouver, ISO, and other styles

11

Šmak, Pavel, Igor Tvaroška, and Jaroslav Koča. "The catalytic reaction mechanism of tyrosylprotein sulfotransferase-1." Physical Chemistry Chemical Physics 23, no. 41 (2021): 23850–60. http://dx.doi.org/10.1039/d1cp03718h.

Full text

Abstract:

The reaction mechanism of TPST-1 was examined using two QM/MM methods: ab initio CPMD metadynamics and potential energy scan. The results support the SN2 reaction mechanism and show the role of the different amino acids in the catalytic mechanism.

APA, Harvard, Vancouver, ISO, and other styles

12

Kwocz, Agnieszka, Jarosław Jan Panek, Aneta Jezierska, Łukasz Hetmańczyk, Andrzej Pawlukojć, Andrzej Kochel, Paweł Lipkowski, and Aleksander Filarowski. "A molecular roundabout: triple cyclically arranged hydrogen bonds in light of experiment and theory." New Journal of Chemistry 42, no. 24 (2018): 19467–77. http://dx.doi.org/10.1039/c8nj04339f.

Full text

Abstract:

This paper dwells on the synthesis and diverse studies of cyclically arranged hydrogen bridges in tris-hydroxy aryl Schiff bases. Experimental (IINS, IR, Raman and X-ray) and theoretical (CPMD, DFTP and DFT) studies of tris-hydroxy aryl Schiff bases have been performed in the solid state.

APA, Harvard, Vancouver, ISO, and other styles

13

Nonnenberg, Christel, Irmgard Frank, and Thomas M. Klapötke. "Die ultraschnelle Kaltreaktion im Treibstoffgemisch Monomethylhydrazin/Distickstofftetroxid: CPMD-Simulation." Angewandte Chemie 116, no. 35 (September 6, 2004): 4686–89. http://dx.doi.org/10.1002/ange.200454093.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Pocheć, Michał, Katarzyna M. Krupka, Jarosław J. Panek, Kazimierz Orzechowski, and Aneta Jezierska. "Intermolecular Interactions and Spectroscopic Signatures of the Hydrogen-Bonded System—n-Octanol in Experimental and Theoretical Studies." Molecules 27, no. 4 (February 11, 2022): 1225. http://dx.doi.org/10.3390/molecules27041225.

Full text

Abstract:

n-Octanol is the object of experimental and theoretical study of spectroscopic signatures and intermolecular interactions. The FTIR measurements were carried out at 293 K for n-octanol and its deuterated form. Special attention was paid to the vibrational features associated with the O-H stretching and the isotope effect. Density Functional Theory (DFT) in its classical formulations was applied to develop static models describing intermolecular hydrogen bond (HB) and isotope effect in the gas phase and using solvent reaction field reproduced by Polarizable Continuum Model (PCM). The Atoms in Molecules (AIM) theory enabled electronic structure and molecular topology study. The Symmetry-Adapted Perturbation Theory (SAPT) was used for energy decomposition in the dimers of n-octanol. Finally, time-evolution methods, namely classical molecular dynamics (MD) and Car-Parrinello Molecular Dynamics (CPMD) were employed to shed light onto dynamical nature of liquid n-octanol with emphasis put on metric and vibrational features. As a reference, CPMD gas phase results were applied. Nuclear quantum effects were included using Path Integral Molecular Dynamics (PIMD) and a posteriori method by solving vibrational Schrödinger equation. The latter applied procedure allowed to study the deuterium isotope effect.

APA, Harvard, Vancouver, ISO, and other styles

15

Wojtkowiak, Kamil, Aneta Jezierska, and Jarosław J. Panek. "Revealing Intra- and Intermolecular Interactions Determining Physico-Chemical Features of Selected Quinolone Carboxylic Acid Derivatives." Molecules 27, no. 7 (April 1, 2022): 2299. http://dx.doi.org/10.3390/molecules27072299.

Full text

Abstract:

The intra- and intermolecular interactions of selected quinolone carboxylic acid derivatives were studied in monomers, dimers and crystals. The investigated compounds are well-recognized as medicines or as bases for further studies in drug design. We employed density functional theory (DFT) in its classical formulation to develop gas-phase and solvent reaction field (PCM) models describing geometric, energetic and electronic structure parameters for monomers and dimers. The electronic structure was investigated based on the atoms in molecules (AIM) and natural bond orbital (NBO) theories. Special attention was devoted to the intramolecular hydrogen bonds (HB) present in the investigated compounds. The characterization of energy components was performed using symmetry-adapted perturbation theory (SAPT). Finally, the time-evolution methods of Car–Parrinello molecular dynamics (CPMD) and path integral molecular dynamics (PIMD) were employed to describe the hydrogen bond dynamics as well as the spectroscopic signatures. The vibrational features of the O-H stretching were studied using Fourier transformation of the autocorrelation function of atomic velocity. The inclusion of quantum nuclear effects provided an accurate depiction of the bridged proton delocalization. The CPMD and PIMD simulations were carried out in the gas and crystalline phases. It was found that the polar environment enhances the strength of the intramolecular hydrogen bonds. The SAPT analysis revealed that the dispersive forces are decisive factors in the intermolecular interactions. In the electronic ground state, the proton-transfer phenomena are not favourable. The CPMD results showed generally that the bridged proton is localized at the donor side, with possible proton-sharing events in the solid-phase simulation of stronger hydrogen bridges. However, the PIMD enabled the quantitative estimation of the quantum effects inclusion—the proton position was moved towards the bridge midpoint, but no qualitative changes were detected. It was found that the interatomic distance between the donor and acceptor atoms was shortened and that the bridged proton was strongly delocalized.

APA, Harvard, Vancouver, ISO, and other styles

16

Sudarmansyah, Ranu, Dedi Koswara, and Nunuy Nurjanah. "NILAI-NILAI PATRIOTISME DALAM CARITA PANTUN MUNDINGLAYA DIKUSUMAH." Widyaparwa 49, no. 2 (December 31, 2021): 402–12. http://dx.doi.org/10.26499/wdprw.v49i2.673.

Full text

Abstract:

As one of the original oral literary works of the archipelago, folklore story has character values and one of them is the value of patriotism. The purpose of this research is to describe the structure of the story and the values of patriotism contained in the Carita pantun Mundinglaya Dikususmah (CPMD). The method used in this research is an analitic descriptive method by (1) describing the structure of the story and (2) exploring the values of patriotism in the Mundinglaya Dikusumah pantun. After analyzing the CPMD story, the results of the research show that (1) the structure of the Mundinglaya Dikusumah folklore have a good theme, good actors (characterizations), a good plot and story setting; (2) there are values of patriotism in the Mundinglaya Dikusumah pantun, including (a) loyalty, (b) courage, (c) willingness to sacrifice, and (d) love for the nation and state. Finally, based on these findings, it can be concluded that the carita pantun Mundinglaya Dikusumah has a story structure that is very supportive of patriotism values which can be useful to become role models for the younger generation.Sebagai salah satu karya sastra lisan asli nusantara, carita pantun memiliki nilai-nilai karakter, di antaranya patriotisme. Penelitian ini bertujuan mendeskripsikan struktur cerita dan nilai-nilai patriotisme yang terdapat pada carita pantun Mundinglaya Dikususmah (CPMD). Metode yang digunakan dalam penelitian ini ialah metode deskriptif analisis dengan cara (1) mendeskripsikan struktur cerita dan (2) menggali nilai-nilai patriotisme dalam carita pantun Mundinglaya Dikusumah. Hasil penelitian menunjukkan bahwa (1) struktur carita pantun Mundinglaya Dikusumah meliputi tema, pelaku (penokohan), alur serta latar cerita yang baik; (2) terdapat nilai-nilai patriotisme dalam carita pantun Mundinglaya Dikusumah, meliputi nilai (a) kesetiaan, (b) keberanian, (c) rela berkorban, serta (d) kecintaan pada bangsa dan negara. Berdasarkan temuan tersebut, dapat disimpulkan bahwa carita pantun Mundinglaya Dikusumah mempunyai struktur cerita yang sangat mendukung terhadap pembentukan nilai-nilai patriotisme yang bisa berguna untuk menjadi suri teladan para generasi muda.

APA, Harvard, Vancouver, ISO, and other styles

17

Kizior, Beata, Mariusz Michalczyk, Jarosław J. Panek, Wiktor Zierkiewicz, and Aneta Jezierska. "Unraveling the Nature of Hydrogen Bonds of “Proton Sponges” Based on Car-Parrinello and Metadynamics Approaches." International Journal of Molecular Sciences 24, no. 2 (January 12, 2023): 1542. http://dx.doi.org/10.3390/ijms24021542.

Full text

Abstract:

The nature of intra- and intermolecular non-covalent interactions was studied in four naphthalene derivatives commonly referred to as “proton sponges”. Special attention was paid to an intramolecular hydrogen bond present in the protonated form of the compounds. The unsubstituted “proton sponge” served as a reference structure to study the substituent influence on the hydrogen bond (HB) properties. We selected three compounds substituted by methoxy, amino, and nitro groups. The presence of the substituents either retained the parent symmetry or rendered the compounds asymmetric. In order to reveal the non-covalent interaction properties, the Hirshfeld surface (HS) was computed for the crystal structures of the studied compounds. Next, quantum-chemical simulations were performed in vacuo and in the crystalline phase. Car–Parrinello molecular dynamics (CPMD), Path Integral Molecular Dynamics (PIMD), and metadynamics were employed to investigate the time-evolution changes of metric parameters and free energy profile in both phases. Additionally, for selected snapshots obtained from the CPMD trajectories, non-covalent interactions and electronic structure were studied. Quantum theory of atoms in molecules (QTAIM) and the Density Overlap Regions Indicator (DORI) were applied for this purpose. It was found based on Hirshfeld surfaces that, besides intramolecular hydrogen bonds, other non-covalent interactions are present and have a strong impact on the crystal structure organization. The CPMD results obtained in both phases showed frequent proton transfer phenomena. The proton was strongly delocalized in the applied time-scale and temperature, especially in the PIMD framework. The use of metadynamics allowed for tracing the free energy profiles and confirming that the hydrogen bonds present in “proton sponges” are Low-Barrier Hydrogen Bonds (LBHBs). The electronic and topological analysis quantitatively described the temperature dependence and time-evolution changes of the electronic structure. The covalency of the hydrogen bonds was estimated based on QTAIM analysis. It was found that strong hydrogen bonds show greater covalency, which is additionally determined by the proton position in the hydrogen bridge.

APA, Harvard, Vancouver, ISO, and other styles

18

Nonnenberg, Christel, Irmgard Frank, and Thomas M. Klapötke. "Ultrafast Cold Reactions in the Bipropellant Monomethylhydrazine/Nitrogen Tetroxide: CPMD Simulations." Angewandte Chemie International Edition 43, no. 35 (September 6, 2004): 4586–89. http://dx.doi.org/10.1002/anie.200454093.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Dopieralski, Przemyslaw D., Zdzislaw Latajka, and Ivar Olovsson. "Proton-transfer dynamics in the (HCO3 −)2 dimer of KHCO3 from Car–Parrinello and path-integrals molecular dynamics calculations." Acta Crystallographica Section B Structural Science 66, no. 2 (February 26, 2010): 222–28. http://dx.doi.org/10.1107/s0108768110002314.

Full text

Abstract:

The proton motion in the (HCO_3^-)2 dimer of KHCO3 at 298 K has been studied with Car–Parrinello molecular dynamics (CPMD) and path-integrals molecular dynamics (PIMD) simulations. According to earlier neutron diffraction studies at 298 K hydrogen is disordered and occupies two positions with an occupancy ratio of 0.804/0.196. A simulation with only one unit cell is not sufficient to reproduce the disorder of the protons found in the experiments. The CPMD results with four cells, 0.783/0.217, are in close agreement with experiment. The motion of the two protons along the O...O bridge is highly correlated inside one dimer, but strongly uncoupled between different dimers. The present results support a mechanism for the disorder which involves proton transfer from donor to acceptor and not orientational disordering of the entire dimer. The question of simultaneous or successive proton transfer in the two hydrogen bonds in the dimer remains unanswered. During the simulation situations with almost simultaneous proton transfer with a time gap of around 1 fs were observed, as well as successive processes where first one proton is transferred and then the second one with a time gap of around 20 fs. The calculated vibrational spectrum is in good agreement with the experimental IR spectrum, but a slightly different assignment of the bands is indicated by the present simulations.

APA, Harvard, Vancouver, ISO, and other styles

20

Andreoni, Wanda, and Alessandro Curioni. "New advances in chemistry and materials science with CPMD and parallel computing." Parallel Computing 26, no. 7-8 (July 2000): 819–42. http://dx.doi.org/10.1016/s0167-8191(00)00014-4.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Wang, Kun, Pan Pan Wu, Tian Tian Zhang, Dian Kai Liu, Chao Hua Dai, Jian Guo Zhang, and Xue Bin Yu. "CPMD Investigations of the Improved Energetic Performance for Lithium Amidoborane doped RDX." ChemistrySelect 4, no. 3 (January 22, 2019): 997–1006. http://dx.doi.org/10.1002/slct.201804063.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Giusepponi, Simone, Massimo Celino, Fabrizio Cleri, and Amelia Montone. "Hydrogen Storage in MgH₂ Matrices: An Ab-Initio Study of Mg-MgH₂ Interface." Solid State Phenomena 139 (April 2008): 23–28. http://dx.doi.org/10.4028/www.scientific.net/ssp.139.23.

Full text

Abstract:

We studied the atomic-level structure of a model Mg-MgH2 interface by means of the Car-Parrinello molecular dynamics method (CPMD). The interface was characterized in terms of total energy calculations, and an estimate of the work of adhesion was given, in good agreement with experimental results on similar systems. Furthermore, the interface was studied in a range of temperatures of interest for the desorption of hydrogen. We determined the diffusivity of atomic hydrogen as a function of the temperature, and give an estimate of the desorption temperature.

APA, Harvard, Vancouver, ISO, and other styles

23

Wang, Nianliang, Kalyan Chakraborty, and Shigeru Kanemitsu. "Unification of Chowla’s Problem and Maillet–Demyanenko Determinants." Mathematics 11, no. 3 (January 28, 2023): 655. http://dx.doi.org/10.3390/math11030655.

Full text

Abstract:

Chowla’s (inverse) problem (CP) is to mean a proof of linear independence of cotangent-like values from non-vanishing of L(1,χ)=∑n=1∞χ(n)n. On the other hand, we refer to determinant expressions for the (relative) class number of a cyclotomic field as the Maillet–Demyanenko determinants (MD). Our aim is to develop the theory of discrete Fourier transforms (DFT) with parity and to unify Chowla’s problem and Maillet–Demyanenko determinants (CPMD) as different-looking expressions of the relative class number via the Dedekind determinant and the base change formula.

APA, Harvard, Vancouver, ISO, and other styles

24

Kułacz, Karol, Michał Pocheć, Aneta Jezierska, and Jarosław J. Panek. "Naphthazarin Derivatives in the Light of Intra- and Intermolecular Forces." Molecules 26, no. 18 (September 17, 2021): 5642. http://dx.doi.org/10.3390/molecules26185642.

Full text

Abstract:

Our long-term investigations have been devoted the characterization of intramolecular hydrogen bonds in cyclic compounds. Our previous work covers naphthazarin, the parent compound of two systems discussed in the current work: 2,3-dimethylnaphthazarin (1) and 2,3-dimethoxy-6-methylnaphthazarin (2). Intramolecular hydrogen bonds and substituent effects in these compounds were analyzed on the basis of Density Functional Theory (DFT), Møller–Plesset second-order perturbation theory (MP2), Coupled Clusters with Singles and Doubles (CCSD) and Car-Parrinello Molecular Dynamics (CPMD). The simulations were carried out in the gas and crystalline phases. The nuclear quantum effects were incorporated a posteriori using the snapshots taken from ab initio trajectories. Further, they were used to solve a vibrational Schrödinger equation. The proton reaction path was studied using B3LYP, ωB97XD and PBE functionals with a 6-311++G(2d,2p) basis set. Two energy minima (deep and shallow) were found, indicating that the proton transfer phenomena could occur in the electronic ground state. Next, the electronic structure and topology were examined in the molecular and proton transferred (PT) forms. The Atoms In Molecules (AIM) theory was employed for this purpose. It was found that the hydrogen bond is stronger in the proton transferred (PT) forms. In order to estimate the dimers’ stabilization and forces responsible for it, the Symmetry-Adapted Perturbation Theory (SAPT) was applied. The energy decomposition revealed that dispersion is the primary factor stabilizing the dimeric forms and crystal structure of both compounds. The CPMD results showed that the proton transfer phenomena occurred in both studied compounds, as well as in both phases. In the case of compound 2, the proton transfer events are more frequent in the solid state, indicating an influence of the environmental effects on the bridged proton dynamics. Finally, the vibrational signatures were computed for both compounds using the CPMD trajectories. The Fourier transformation of the autocorrelation function of atomic velocity was applied to obtain the power spectra. The IR spectra show very broad absorption regions between 700 cm−1–1700 cm−1 and 2300 cm−1–3400 cm−1 in the gas phase and 600 cm−1–1800 cm−1 and 2200 cm−1–3400 cm−1 in the solid state for compound 1. The absorption regions for compound 2 were found as follows: 700 cm−1–1700 cm−1 and 2300 cm−1–3300 cm−1 for the gas phase and one broad absorption region in the solid state between 700 cm−1 and 3100 cm−1. The obtained spectroscopic features confirmed a strong mobility of the bridged protons. The inclusion of nuclear quantum effects showed a stronger delocalization of the bridged protons.

APA, Harvard, Vancouver, ISO, and other styles

25

Jóźwiak, Kinga, Aneta Jezierska, Jarosław J. Panek, Andrzej Kochel, and Aleksander Filarowski. "Inter- vs. Intra-Molecular Hydrogen Bond in Complexes of Nitrophthalic Acids with Pyridine." International Journal of Molecular Sciences 24, no. 6 (March 9, 2023): 5248. http://dx.doi.org/10.3390/ijms24065248.

Full text

Abstract:

This study covers the analysis of isomeric forms of nitrophthalic acids with pyridine. This work dwells on the complementary experimental (X-ray, IR and Raman) and theoretical (Car-Parrinello Molecular Dynamics (CPMD) and Density Functional Theory (DFT)) studies of the obtained complexes. The conducted studies showed that steric repulsion between the nitro group in ortho-position and the carboxyl group causes significant isomeric changes. Modeling of the nitrophthalic acid—pyridine complex yielded a short strong intramolecular hydrogen bond (SSHB). The transition energy from the isomeric form with an intermolecular hydrogen bond to the isomeric form with an intramolecular hydrogen bond was estimated.

APA, Harvard, Vancouver, ISO, and other styles

26

Yan, Han, and Pei Wang. "Adsorption and Diffusion of Aluminum, Gallium and Indium Atoms on Semi-Polar Gallium Nitride Substrate Surface: A First Principle Simulation." Advanced Materials Research 1015 (August 2014): 598–601. http://dx.doi.org/10.4028/www.scientific.net/amr.1015.598.

Full text

Abstract:

The first principles simulations are performed to investigate the adsorption and diffusion of aluminum, gallium and indium atoms on semi-polar gallium nitrides surface, the calculations are performed by using the Car–Parrinello molecular dynamics (CPMD) method. The aluminum ad-atoms adsorption in path 1 and path 3 are much stable than in path 2. The maximum adsorption energy of path1, path2 and path3 are different, which reveal that a different barrier energy pathway between indium ad-atom diffuse along path 1, path2 and path3. Our calculation results reveal that diffusion barriers of aluminum, gallium and indium atoms on semi-polar gallium nitride surface are anisotropy.

APA, Harvard, Vancouver, ISO, and other styles

27

Kizior, Beata, Jarosław J. Panek, Bartłomiej M. Szyja, and Aneta Jezierska. "Structure-Property Relationship in Selected Naphtho- and Anthra-Quinone Derivatives on the Basis of Density Functional Theory and Car–Parrinello Molecular Dynamics." Symmetry 13, no. 4 (March 29, 2021): 564. http://dx.doi.org/10.3390/sym13040564.

Full text

Abstract:

Intra- and inter-molecular interactions were studied in 2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone and 1,4-dihydroxy-anthraquinone to shed more light on the molecular assembly phenomena. The electronic ground and excited states features of the compounds were investigated to find structure-property dependencies. The theoretical study was carried out on the basis of Density Functional Theory (DFT), its Time-Dependent (TD-DFT) extension, and using Car–Parrinello Molecular Dynamics (CPMD). In order to show how the environmental effects modulate the physico-chemical properties, the simulations were performed in vacuo, with the solvent reaction field (Polarizable Continuum Model (PCM) and water as a solvent) and crystalline phase. The intramolecular hydrogen bonds and the bridged proton dynamics were analyzed in detail. The aromatic rings and electronic structure changes were estimated using the Harmonic Oscillator Model of Aromaticity (HOMA) and Atoms in Molecules (AIM) theory. The Symmetry-Adapted Perturbation Theory (SAPT) was employed for interaction energy decomposition in the studied dimers and trimers. It was found that the presence of a polar solvent decreased the energy barrier for the bridged proton transfer. However, it did not significantly affect the aromaticity and electronic structure. The SAPT results showed that the mutual polarization of the monomers in the dimer was weak and that the dispersion was responsible for most of the intermolecular attraction. The intermolecular hydrogen bonds seem to be much weaker than the intramolecular bridges. The TD-DFT results confirmed that the electronic excitations do not play any significant role in the intramolecular proton transfer. The CPMD results indicated that the protons are very labile in the hydrogen bridges. Short proton transfer and proton-sharing events were observed, and a correlation between them in the twin bridges was noticed, especially for the first investigated compound.

APA, Harvard, Vancouver, ISO, and other styles

28

Raczyński, Kamil, Andrzej Pihut, Jarosław J. Panek, and Aneta Jezierska. "Competition of Intra- and Intermolecular Forces in Anthraquinone and Its Selected Derivatives." Molecules 26, no. 11 (June 6, 2021): 3448. http://dx.doi.org/10.3390/molecules26113448.

Full text

Abstract:

Intra- and intermolecular forces competition was investigated in the 9,10-anthraquinone (1) and its derivatives both in vacuo and in the crystalline phase. The 1,8-dihydroxy-9,10-anthraquinone (2) and 1,8-dinitro-4,5-dihydroxy-anthraquinone (3) contain Resonance-Assisted Hydrogen Bonds (RAHBs). The intramolecular hydrogen bonds properties were studied in the electronic ground and excited states employing Møller-Plesset second-order perturbation theory (MP2), Density Functional Theory (DFT) method in its classical formulation as well as its time-dependent extension (TD-DFT). The proton potential functions were obtained via scanning the OH distance and the dihedral angle related to the OH group rotation. The topological analysis was carried out on the basis of theories of Atoms in Molecules (AIM—molecular topology, properties of critical points, AIM charges) and Electron Localization Function (ELF—2D maps showing bonding patterns, calculation of electron populations in the hydrogen bonds). The Symmetry-Adapted Perturbation Theory (SAPT) was applied for the energy decomposition in the dimers. Finally, Car–Parrinello molecular dynamics (CPMD) simulations were performed to shed light onto bridge protons dynamics upon environmental influence. The vibrational features of the OH stretching were revealed using Fourier transformation of the autocorrelation function of atomic velocity. It was found that the presence of OH and NO2 substituents influenced the geometric and electronic structure of the anthraquinone moiety. The AIM and ELF analyses showed that the quantitative differences between hydrogen bonds properties could be neglected. The bridged protons are localized on the donor side in the electronic ground state, but the Excited-State Intramolecular Proton Transfer (ESIPT) was noticed as a result of the TD-DFT calculations. The hierarchy of interactions determined by SAPT method indicated that weak hydrogen bonds play modifying role in the organization of these crystal structures, but primary ordering factor is dispersion. The CPMD crystalline phase results indicated bridged proton-sharing in the compound 2.

APA, Harvard, Vancouver, ISO, and other styles

29

Piękoś, Patrycja, Aneta Jezierska, Jarosław J. Panek, Eugene A. Goremychkin, Alexander F. Pozharskii, Alexander S. Antonov, Peter M. Tolstoy, and Aleksander Filarowski. "Symmetry/Asymmetry of the NHN Hydrogen Bond in Protonated 1,8-Bis(dimethylamino)naphthalene." Symmetry 12, no. 11 (November 23, 2020): 1924. http://dx.doi.org/10.3390/sym12111924.

Full text

Abstract:

Experimental and theoretical results are presented based on vibrational spectra and motional dynamics of 1,8-bis(dimethylamino)naphthalene (DMAN) and its protonated forms (DMANH+ and the DMANH+ HSO4− complex). The studies of these compounds have been performed in the gas phase and solid-state. Spectroscopic investigations were carried out by infrared spectroscopy (IR), Raman, and incoherent inelastic neutron scattering (IINS) experimental methods. Density functional theory (DFT) and Car–Parrinello molecular dynamics (CPMD) methods were applied to support our experimental findings. The fundamental investigations of hydrogen bridge vibrations were accomplished on the basis of isotopic substitutions (NH → ND). Special attention was paid to the bridged proton dynamics in the DMANH+ complex, which was found to be affected by interactions with the HSO4− anion.

APA, Harvard, Vancouver, ISO, and other styles

30

Fadeeva, Yuliya A., Irina V. Fedorova, Mikhail A. Krestyaninov, and Lyubov P. Safonova. "Structural characterization of H3PO3 and H3PO4 acids solutions in DMF: Spectral analysis and CPMD simulation." Journal of Molecular Liquids 300 (February 2020): 112342. http://dx.doi.org/10.1016/j.molliq.2019.112342.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Hutter, Jürg, and Alessandro Curioni. "Dual-level parallelism for ab initio molecular dynamics: Reaching teraflop performance with the CPMD code." Parallel Computing 31, no. 1 (January 2005): 1–17. http://dx.doi.org/10.1016/j.parco.2004.12.004.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Saukkoriipi, Jaakko J., and Kari Laasonen. "Density Functional Studies of the Hydrolysis of Aluminum (Chloro)Hydroxide in Water with CPMD and COSMO." Journal of Physical Chemistry A 112, no. 43 (October 30, 2008): 10873–80. http://dx.doi.org/10.1021/jp804176v.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Wang, Kun, Dian Kai Liu, Pan Pan Wu, Xue Bin Yu, Long Jiu Cheng, and Jian Guo Zhang. "How hydrogen-storage material affects the decomposition of nitramine explosive: CPMD investigations of LAB-doped CL20." International Journal of Hydrogen Energy 43, no. 43 (October 2018): 19825–40. http://dx.doi.org/10.1016/j.ijhydene.2018.08.146.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Hofbauer, Florian, and Irmgard Frank. "CPMD Simulation of a Bimolecular Chemical Reaction: Nucleophilic Attack of a Disulfide Bond under Mechanical Stress." Chemistry - A European Journal 18, no. 51 (October 30, 2012): 16332–38. http://dx.doi.org/10.1002/chem.201202065.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Wang, Kun, Jian-Guo Zhang, and Xu-Qiang Lang. "The mechanism of controllable dehydrogenation: CPMD study of M(BH4)x(NH3)y (M = Li, Mg) decomposition." Physical Chemistry Chemical Physics 18, no. 10 (2016): 7015–18. http://dx.doi.org/10.1039/c5cp06808h.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Tomar, Vikas. "First Principles Calculations of Interfaces in Ultra High Temperature Ceramics." Advances in Science and Technology 89 (October 2014): 100–108. http://dx.doi.org/10.4028/www.scientific.net/ast.89.100.

Full text

Abstract:

This work focuses on understanding the influence of temperature on correlations between thermal conduction and mechanical strength in material interfaces including a high temperature material interface. Analyses examine single crystal ZrB2, single crystal SiC, and a <0001>-<111> ZrB2-SiC interface using a framework based on Car Parrinello molecular dynamics (CPMD)ab-initiosimulation method from 500 K to 2500 K. Analyses indicate that the strength reduction with increase in temperature is strongly correlated to phonon and electron thermal diffusivity change. With increase in temperature, phonon thermal diffusivity increases in the case of ZrB2 and reduces in the cases of SiC as well as the interface. Electron contribution to thermal diffusivity increases with temperature increase in the case of interface. Examination of change in thermal properties at different mechanical strain levels reveals that the mechanisms of strength and thermal property change with increase in temperature may be similar to the mechanisms responsible for property change with change in applied strain.

APA, Harvard, Vancouver, ISO, and other styles

37

Pocheć, Michał, Karol Kułacz, Jarosław J. Panek, and Aneta Jezierska. "How Substitution Combines with Non-Covalent Interactions to Modulate 1,4-Naphthoquinone and Its Derivatives Molecular Features—Multifactor Studies." International Journal of Molecular Sciences 22, no. 19 (September 26, 2021): 10357. http://dx.doi.org/10.3390/ijms221910357.

Full text

Abstract:

Substitution is well-known to modulate the physico-chemical properties of molecules. In this study, a combined, multifactor approach was employed to determine a plethora of substitution patterns using –Br and –O-H in 1,4-naphthoquinone and its derivatives. On the basis of classical Density Functional Theory (DFT), 25 models divided into three groups were developed. The first group contains 1,4-naphthoquinone and its derivatives substituted only by –Br. The second group consists of compounds substituted by –Br and one –O-H group. As a result of the substitution, an intramolecular hydrogen bond was formed. The third group also contains –Br as a substituent, but two –O-H groups were introduced and two intramolecular hydrogen bonds were established. The simulations were performed at the ωB97XD/6-311++G(2d,2p) level of theory. The presence of substituents influenced the electronic structure of the parent compound and its derivatives by inductive effects, but it also affected the geometry of the 2 and 3 groups, due to the intramolecular hydrogen bonding and the formation of a quasi-ring/rings. The static DFT models were applied to investigate the aromaticity changes in the fused rings based on the Harmonic Oscillator Model of Aromaticity (HOMA). The OH stretching was detected for the compounds from groups 2 and 3 and further used to find correlations with energetic parameters. The evolution of the electronic structure was analyzed using Hirshfeld atomic charges and the Substituent Active Region (cSAR) parameter. The proton reaction path was investigated to provide information on the modulation of hydrogen bridge properties by diverse substitution positions on the donor and acceptor sides. Subsequently, Car–Parrinello Molecular Dynamics (CPMD) was carried out in the double-bridged systems (group 3) to assess the cooperative effects in double –O-H-substituted systems. It was determined that the –O-H influence on the core of the molecule is more significant than that of –Br, but the latter has a major impact on the bridge dynamics. The competitive or synergic effect of two –Br substituents was found to depend on the coupling between the intramolecular hydrogen bridges. Thus, the novel mechanism of a secondary (cooperative) substituent effect was established in the double-bridged systems via DFT and CPMD results comparison, consisting of a mediation of the bromine substitutions’ influence by the cooperative proton transfer events in the hydrogen bridges.

APA, Harvard, Vancouver, ISO, and other styles

38

Lian, Peng, Jue Li, Dong-Qi Wang, and Dong-Qing Wei. "Car–Parrinello Molecular Dynamics/Molecular Mechanics (CPMD/MM) Simulation Study of Coupling and Uncoupling Mechanisms of Cytochrome P450cam." Journal of Physical Chemistry B 117, no. 26 (June 20, 2013): 7849–56. http://dx.doi.org/10.1021/jp312107r.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Zang, Jin-Liang, Quanzi Yuan, Feng-Chao Wang, and Ya-Pu Zhao. "A comparative study of Young’s modulus of single-walled carbon nanotube by CPMD, MD and first principle simulations." Computational Materials Science 46, no. 3 (September 2009): 621–25. http://dx.doi.org/10.1016/j.commatsci.2009.04.007.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Xia, Fei-Fei, Dewen Zeng, Hai-Bo Yi, and Chunhui Fang. "Direct Contact versus Solvent-Shared Ion Pairs in Saturated NiCl2 Aqueous Solution: A DFT, CPMD, and EXAFS Investigation." Journal of Physical Chemistry A 117, no. 35 (August 23, 2013): 8468–76. http://dx.doi.org/10.1021/jp405168r.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Geicke, Jan, Ingo-Peter Lorenz, Petra Mürschel, and Kurt Polbom. "Dppa als Komplexligand: Metall-Koordination und P-N-Spaltung in Komplexen des Typs [CpM(L)dppa]X (M = Fe, Mn; L = CO, NO) / Dppa as a Ligand: Metal Coordination and P-N Cleavage in Complexes of the Type [CpM(L)dppa]X (M = Fe, Mn; L = CO, NO)." Zeitschrift für Naturforschung B 52, no. 5 (May 1, 1997): 593–603. http://dx.doi.org/10.1515/znb-1997-0509.

Full text

Abstract:

Abstract The reactions of [CpMn(CO)2(NO)]BF4 or CpFe(CO)2Cl with PPh2NHR (R = Ph, PPh2) lead to the salts [CpML(CO)PPh2NHR]X with monodentate aminophosphine ligands. In the case of R = PPh2 (= dppa) the complexes [CpML(dppa)]X with bidentate dppa are also formed. The salt [CpFe(CO)(dppa)]Cl can be deprotonated to give the neutral complex CpFe(CO){(PPh2)2N)} with the diphosphinoamide ligand, which can be N-alkylated by Mel to afford [CpFe(CO){(PPh2)2NMe}]I. The complex [CpMn(NO)(dppa)]BF4 undergoes a P-N cleavage reaction by the solvent methanol to form [CpMn(NO)(PPh2NH2)(PPh2OMe)]BF4. The non-chelated complexes [CpFe(CO)2PPh2NHR]Cl are deprotonated by DBU to give the neutral ferrioiminophosphoranes CpFe(CO)2PPh2 = NR. For R = PPh2 photolysis leads to CO-elimination and to CpFe(CO)(PPh2NPPh2). CpFe(CO)2PPh2NPPh2 can be alkylated by Mel or metallated by CpFe(CO)2Cl to form [CpFe(CO)2PPh2NPPh2Me]I or [CpFe(CO)2PPh2NPPh2(CO)2FeCp]Cl, respectively. Oxidation of CpFe(CO)2PPh2NPPh2 is possible by (SiMe3)2O2, sulfur, or selenium to lead to the neutral complexes CpFe(CO)2PPh2=NPPh2 = E (E = O, S, Se) with a heterodiene system. The IR and NMR spectra of all species as well as the X-ray structures of the complexes [CpFe(CO)dppa]Cl, [CpMn(NO)dppa]BF4 and [CpMn(NO)(PPh2NH2)(PPh2OMe)]BF4 are reported and discussed.

APA, Harvard, Vancouver, ISO, and other styles

42

Williams, Robert W., and Daksh Malhotra. "van der Waals corrections to density functional theory calculations: Methane, ethane, ethylene, benzene, formaldehyde, ammonia, water, PBE, and CPMD." Chemical Physics 327, no. 1 (August 2006): 54–62. http://dx.doi.org/10.1016/j.chemphys.2006.03.037.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

Zhang, Tiantian, Longjiu Cheng, Jianguo Zhang, and Kun Wang. "CPMD investigation of α-RDX and ε-CL-20: the transition of deflagration to detonation depending on the self-produced radicals." Physical Chemistry Chemical Physics 22, no. 14 (2020): 7421–29. http://dx.doi.org/10.1039/d0cp00050g.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Alnemrat, Sufian, Joseph P. Hooper, Lidong Guo, and Zongbi Bao. "Structural and bonding properties of small hydrocarbons inside Ca(squarate)-metal organic framework: ab-initio study." Journal of Physics Communications 6, no. 4 (April 1, 2022): 045001. http://dx.doi.org/10.1088/2399-6528/ac53f9.

Full text

Abstract:

Abstract Ab−initio Molecular Dynamic (MD) and static Density Functional Theory (DFT) are used to study the structural and bonding properties of small hydrocarbon adsorbates inside Ca(squarate)−Metal Organic Framework (MOF). Car−Parrinello Molecular Dynamics (CPMD) simulations of a single−adsorbate−MOF structure are used to obtain the adsorbate most preferred site of adsorption. This site is used for further structural and bonding analyses using static DFT. Unlike many other MOFs; we found that the Ca(squarate)−MOF physisorbs and weakly binds small adsorbate molecules such as C2H2, C2H4, C2H6, and C3H8 with no observed charge transfer and minimal hybridization with the MOF orbitals. No covalent bonding is seen near the preferred site of adsorption. The calculated binding energies decreases as the H content in the adsorbate molecule increases and found to be −18.71 kJ/mol, −18.14 kJ/mol, −15.75 kJ/mol, and—4.47 kJ/mol for C2H2, C2H4, C2H6, and C3H8 molecules respectively. Density of State (DOS) and a Crystal Orbital Overlap Population (COOP) analyses show that the interactions between C and H atoms in the molecule and C and O atoms in the MOF have antibonding characteristics near the Fermi level. These antibonding states tend to destabilize the overall electronic structure of the combined adsorbate/MOF system and hence decrease the binding energies of these adsorbates inside the MOF.

APA, Harvard, Vancouver, ISO, and other styles

45

Wojtkowiak, Kamil, and Aneta Jezierska. "Exploring the Dynamical Nature of Intermolecular Hydrogen Bonds in Benzamide, Quinoline and Benzoic Acid Derivatives." Molecules 27, no. 24 (December 13, 2022): 8847. http://dx.doi.org/10.3390/molecules27248847.

Full text

Abstract:

The hydrogen bonds properties of 2,6-difluorobenzamide, 5-hydroxyquinoline and 4-hydroxybenzoic acid were investigated by Car–Parrinello and path integral molecular dynamics (CPMD and PIMD), respectively. The computations were carried out in vacuo and in the crystalline phase. The studied complexes possess diverse networks of intermolecular hydrogen bonds (N-H…O, O-H…N and O-H…O). The time evolution of hydrogen bridges gave a deeper insight into bonds dynamics, showing that bridged protons are mostly localized on the donor side; however, the proton transfer phenomenon was registered as well. The vibrational features associated with O-H and N-H stretching were analyzed on the basis of the Fourier transform of the atomic velocity autocorrelation function. The spectroscopic effects of hydrogen bond formation were studied. The PIMD revealed quantum effects influencing the hydrogen bridges providing more accurate free energy sampling. It was found that the N…O or O…O interatomic distances decreased (reducing the length of the hydrogen bridge), while the O-H or N-H covalent bond was elongated, which led to the increase in the proton sharing. Furthermore, Quantum Theory of Atoms in Molecules (QTAIM) was used to give insight into electronic structure parameters. Finally, Symmetry-Adapted Perturbation Theory (SAPT) was employed to estimate the energy contributions to the interaction energy of the selected dimers.

APA, Harvard, Vancouver, ISO, and other styles

46

Lanzillo, N. A., E. B. Watson, J. B. Thomas, S. K. Nayak, and A. Curioni. "Near-surface controls on the composition of growing crystals: Car–Parrinello molecular dynamics (CPMD) simulations of Ti energetics and diffusion in alpha quartz." Geochimica et Cosmochimica Acta 131 (April 2014): 33–46. http://dx.doi.org/10.1016/j.gca.2014.01.015.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Sahoo, Sudhir K., and Nisanth N. Nair. "CPMD/GULP QM/MM interface for modeling periodic solids: Implementation and its application in the study of Y-zeolite supported Rh n clusters." Journal of Computational Chemistry 37, no. 18 (April 19, 2016): 1657–67. http://dx.doi.org/10.1002/jcc.24379.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Modi, Chirag, Punit Bhatt, Urvesh Patel, Harshad Patel, and Kajal Pandya. "Immunomodulatory effect of the hydroalcoholic extract of Abrus precatorius L. leaves against cyclophosphamide-induced immunosuppression in mice." Archives of Biological Sciences 73, no. 2 (2021): 279–90. http://dx.doi.org/10.2298/abs210219022m.

Full text

Abstract:

This study presents the immunomodulatory potential of Abrus precatorius Linn. (Indian wild licorice) leaves. A hydroalcoholic extract of A. precatorius leaves (EAPL) was prepared by maceration. Thirty male mice were divided into five groups as follows: control group, model control group (cyclophosphamide-treated), and three treatment groups (treated with EAPL at doses of 100, 200 and 300 mg/kg, per os, daily for 14 days). Parameters, including hematological, biochemical, organ indices, hemagglutination test (HA titer), delayed-type hypersensitivity (DTH), interleukin-2 (IL-2) level, splenocyte proliferation and liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) analysis were evaluated. Histopathological examination was carried out for the spleen, kidney and liver. Cyclophosphamide (CPMD)-induced changes in white blood cells, lymphocytes and platelets were improved in the treatment groups. Total protein and albumin levels in the treatment groups were significantly higher. EAPL treatment significantly stimulated splenic T-lymphocytemediated proliferation. Neutrophil adhesion was insignificantly decreased in the model control group compared to the normal control group, which was slightly improved by EAPL treatment. EAPL treatment significantly improved the HA titer and cell-mediated immunity, which is an indication of antibody production. The IL-2 level was significantly higher in the treatment groups that received 200 and 300 mg/kg EAPL. LC-QTOF-MS analysis of EAPL showed the presence of flavonoids, lignans, iridoids and phenolic glycosides. These results suggest that A. precatorius leaves are a good candidate for a new immunomodulatory herbal formulation.

APA, Harvard, Vancouver, ISO, and other styles

49

Stephen Oladeji, Babatunde, and Adeniran Omotoso Badmus. "Physico-chemical and sensory properties of cereal/legume-substituted cocoa-based beverage." Nutrition & Food Science 44, no. 5 (September 2, 2014): 400–406. http://dx.doi.org/10.1108/nfs-02-2013-0022.

Full text

Abstract:

Purpose – The purpose of this paper is to develop a cereal/legume-substituted cocoa-based beverage using cocoa powder, malted sorghum flour, soybean flour and defatted melon seed flour and to evaluate their physico-chemical, nutritional and sensory properties. Design/methodology/approach – Malted sorghum was prepared; flours of soybean and defatted melon were also prepared separately. Two samples were formulated, the first formulation tagged CPM1 contained 60, 10, 20 and 10 per cent of cocoa powder, malted sorghum, soybean flour and melon flour, respectively, and the second sample tagged CPM2 contained 65, 05, 20 and 10 per cent of cocoa powder, malted sorghum, soybean flour and melon flour, respectively. A commercial product (Noble Vita) was purchased from local market as reference sample. Findings – Protein contents of formulated samples (16.93 and10.58 per cent for samples CPM1 and CPM2, respectively) are higher than that of the Noble Vita (6.35 per cent). The vitamin C content of the formulated samples was found to be 13.38 and 13.50 mg/100 g, an improvement from that of the reference sample (6.13 mg/100 g). Significant difference exists in the overall acceptability between the formulated samples and the reference sample (p < 0.05), and the formulated samples were more acceptable. Originality/value – Formulated samples are nutritionally richer than the reference sample and that they are capable of supplying limiting nutrients in the diet of majority in the developing countries.

APA, Harvard, Vancouver, ISO, and other styles

50

Machado, Hugo G., Flávio O. Sanches-Neto, Nayara D. Coutinho, Kleber C. Mundim, Federico Palazzetti, and Valter H. Carvalho-Silva. "“Transitivity”: A Code for Computing Kinetic and Related Parameters in Chemical Transformations and Transport Phenomena." Molecules 24, no. 19 (September 25, 2019): 3478. http://dx.doi.org/10.3390/molecules24193478.

Full text

Abstract:

The Transitivity function, defined in terms of the reciprocal of the apparent activation energy, measures the propensity for a reaction to proceed and can provide a tool for implementing phenomenological kinetic models. Applications to systems which deviate from the Arrhenius law at low temperature encouraged the development of a user-friendly graphical interface for estimating the kinetic and thermodynamic parameters of physical and chemical processes. Here, we document the Transitivity code, written in Python, a free open-source code compatible with Windows, Linux and macOS platforms. Procedures are made available to evaluate the phenomenology of the temperature dependence of rate constants for processes from the Arrhenius and Transitivity plots. Reaction rate constants can be calculated by the traditional Transition-State Theory using a set of one-dimensional tunneling corrections (Bell (1935), Bell (1958), Skodje and Truhlar and, in particular, the deformed ( d -TST) approach). To account for the solvent effect on reaction rate constant, implementation is given of the Kramers and of Collins–Kimball formulations. An input file generator is provided to run various molecular dynamics approaches in CPMD code. Examples are worked out and made available for testing. The novelty of this code is its general scope and particular exploit of d -formulations to cope with non-Arrhenius behavior at low temperatures, a topic which is the focus of recent intense investigations. We expect that this code serves as a quick and practical tool for data documentation from electronic structure calculations: It presents a very intuitive graphical interface which we believe to provide an excellent working tool for researchers and as courseware to teach statistical thermodynamics, thermochemistry, kinetics, and related areas.

APA, Harvard, Vancouver, ISO, and other styles

We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!