Log in

Relevant bibliographies by topics / Quantum Clusters / Journal articles

Journal articles on the topic 'Quantum Clusters'

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

Author: Grafiati

Published: 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 'Quantum Clusters.'

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

Ma, H., B. Chen, Z. Guo, and H. Li. "Development of quantum network based on multiparty quantum secret sharing." Canadian Journal of Physics 86, no. 9 (September 1, 2008): 1097–101. http://dx.doi.org/10.1139/p08-047.

Full text

Abstract:

In this paper, we develop a quantum network with a mutual quantum secure direct communication scheme based on multiparty quantum secret sharing. This quantum network, assumed to contain clusters S, M, and D, shares a sequence of single photons and Greenberger–Horne–Zeilinger (GHZ) states. Each cluster is made of the same or similar quantum nodes gathered or occurring closely together. The feature of this scheme is that the communication between two clusters depends on the agreement of the third cluster. We also prove that such a quantum network is unconditionally secure.PACS Nos.: 03.67.–Dd, 03.67.–Hk, 89.70.–a

APA, Harvard, Vancouver, ISO, and other styles

2

Weigend, Florian, and Reinhart Ahlrichs. "Quantum chemical treatments of metal clusters." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 368, no. 1915 (March 28, 2010): 1245–63. http://dx.doi.org/10.1098/rsta.2009.0268.

Full text

Abstract:

This work focuses on finding and rationalizing the building principles of clusters with approximately 300 atoms of different types of metals: main group elements (Al, Sn), alkaline earth metals (Mg), transition metals (Pd) and clusters consisting of two different elements (Ir and Pt). Two tools are inevitable for this purpose: (i) quantum chemical methods that are able to treat a given cluster with both sufficient accuracy and efficiency and (ii) algorithms that are able to systematically scan the (3 n −6)-dimensional potential surface of an n -atomic cluster for promising isomers. Currently, the only quantum chemical method that can be applied to metal clusters is density functional theory (DFT). Other methods either do not account for the multi-reference character of metal clusters or are too expensive and thus can be applied only to clusters of very few atoms, which usually is not sufficient for studying the building principles. The accuracy of DFT is not known a priori , but extrapolations to bulk values from calculated series of data show satisfying agreement with experimental data. For scans of the potential surface, simulated annealing techniques or genetic algorithms were used for the smaller clusters (approx. 20–30 atoms), and for the larger clusters considerations were restricted to selected packings and shapes. For the mixed-metallic clusters, perturbation theory turned out to be efficient and successful for finding the most promising distributions of the two atom types at the different sites.

APA, Harvard, Vancouver, ISO, and other styles

3

Sadrara, Mahdiyeh, and MirFaez Miri. "Collective cloaking of a cluster of electrostatically defined core–shell quantum dots in graphene." Journal of Physics: Condensed Matter 34, no. 11 (January 4, 2022): 115703. http://dx.doi.org/10.1088/1361-648x/ac4440.

Full text

Abstract:

Abstract We study cloaking of a cluster of electrostatically defined core–shell quantum dots in graphene. Guided by the generalized multiparticle Mie theory, the Dirac electron scattering from a cluster of quantum dots is addressed. Indeed distant quantum dots may experience a sort of individual cloaking. But despite the multiple scattering of an incident electron from a set of adjacent quantum dots, collective cloaking may happen. Via a proper choice of the radii and bias voltages of shells, two most important scattering coefficients and hence the scattering efficiency of the cluster dramatically decrease. Energy-selective electron cloaks are realizable. More importantly, clusters simultaneously transparent to electrons of different energies, are achievable. Being quite sensitive to applied bias voltages, clusters of core–shell quantum dots may be used to develop switches with high on-off ratios.

APA, Harvard, Vancouver, ISO, and other styles

4

Choi, Jaeho, Seunghyeok Oh, and Joongheon Kim. "Energy-Efficient Cluster Head Selection via Quantum Approximate Optimization." Electronics 9, no. 10 (October 13, 2020): 1669. http://dx.doi.org/10.3390/electronics9101669.

Full text

Abstract:

This paper proposes an energy-efficient cluster head selection method in the wireless ad hoc network by using a hybrid quantum-classical approach. The wireless ad hoc network is divided into several clusters via cluster head selection, and the performance of the network topology depends on the distribution of these clusters. For an energy-efficient network topology, none of the selected cluster heads should be neighbors. In addition, all the selected cluster heads should have high energy-consumption efficiency. Accordingly, an energy-efficient cluster head selection policy can be defined as a maximum weight independent set (MWIS) formulation. The cluster head selection policy formulated with MWIS is solved by using the quantum approximate optimization algorithm (QAOA), which is a hybrid quantum-classical algorithm. The accuracy of the proposed energy-efficient cluster head selection via QAOA is verified via simulations.

APA, Harvard, Vancouver, ISO, and other styles

5

NOZUE, Y., T. KODAIRA, S. OHWASHI, N. TOGASHI, and O. TERASAKI. "FERROMAGNETISM OF ALKALI-METAL CLUSTERS INCORPORATED IN THE PERIODIC SPACE OF ZEOLITE LTA." Surface Review and Letters 03, no. 01 (February 1996): 701–6. http://dx.doi.org/10.1142/s0218625x96001261.

Full text

Abstract:

Magnetic properties are reported for rubidium and potassium clusters arrayed in a simple-cubic structure in zeolite LTA crystal. A ferromagnetism is observed, although no magnetic element is contained there. The result clearly indicates the intercluster interaction. The ferromagnetic properties vary depending on the average number of ns electrons of cluster. Optical properties reveal quantum electronic levels of cluster. The ferromagnetism is interpreted qualitatively in terms of the itinerant electron model based on the quantum levels of cluster. The magnetic properties of various clusters observed in zeolites are discussed from the microscopic point of view.

APA, Harvard, Vancouver, ISO, and other styles

6

SHOKRI, B., A. R. NIKNAM, and V. KRAINOV. "Cluster structure effects on the interaction of an ultrashort intense laser field with large clusters." Laser and Particle Beams 22, no. 1 (March 2004): 13–18. http://dx.doi.org/10.1017/s0263034604221036.

Full text

Abstract:

The structure of large clusters such as neutral clusters, metallic clusters, and clusters ion is investigated. Furthermore, the electron distribution of large clusters when they are irradiated by an intense ultrashort laser pulse is treated. The cluster excitation results from the interaction of the electron subsystem with the laser field. Analyzing the quantum metallic cluster proves that its properties differ essentially from the properties of a classical small metallic sphere. The eigen frequency of the surface oscillation of a cluster is obtained and it is shown that it is lower than Mie frequency because of Thomas–Fermi screening.

APA, Harvard, Vancouver, ISO, and other styles

7

Fu, Liu Qiang, and Hong Wei Zhang. "Dynamic Clustering Based on Quantum-Behaved Particle Swarm Optimization." Advanced Materials Research 798-799 (September 2013): 808–13. http://dx.doi.org/10.4028/www.scientific.net/amr.798-799.808.

Full text

Abstract:

Most clustering algorithm require the number of cluster as a priori knowledge to input, and metrics based on Euclidean distance is good results with only circular clusters. An improved dynamic clustering algorithm was presented, which combines the quantum particle swarm algorithm with k-means algorithm by improving the encoding of quantum particles and the introduction of new distance metric rules. The algorithm has a quantum-behaved particle swarm global search capability. And In order to accelerate the convergence speed, the k-means algorithm is used to optimize every particle .Through the adjustment of the value of the fitness function, our algorithm can search for the optimal clustering number of clusters, so the number of clusters and centers are not subject to subjective factors. Extensive experiments verified the effectiveness of the algorithm.

APA, Harvard, Vancouver, ISO, and other styles

8

Gläßel, Susanne, Viktar Kireyeu, Vadim Voronyuk, Jörg Aichelin, Christoph Blume, Elena Bratkovskaya, Gabriele Coci, Vadim Kolesnikov, and Michael Winn. "Dynamical cluster and hypernuclei production in heavy-ion collisions." EPJ Web of Conferences 259 (2022): 11003. http://dx.doi.org/10.1051/epjconf/202225911003.

Full text

Abstract:

We study light cluster and hypernuclei production in heavy-ion collisions from SIS to RHIC energies based on the n-body dynamical transport approach PHQMD (Parton-Hadron-Quantum-Molecular-Dynamics). In PHQMD clusters are formed dynamically due to the interactions between baryons described on the basis of Quantum Molecular Dynamics (QMD) which allows to propagate the n-body Wigner density and n-body correlations in phase-space, which is essential for the cluster formation. The clusters are identified by the MST (Minimum Spanning Tree) or the SACA (‘Simulated Annealing Cluster Algorithm’) algorithm which finds the most-bound configuration of nucleons and clusters. Collisions among hadrons as well as Quark-Gluon-Plasma formation and parton dynamics in PHQMD are treated in the same way as in the PHSD (Parton-Hadron-String-Dynamics) transport approach. We study the time evolution of the cluster formation in the expanding medium and the stability of the clusters. We present a comparison of the PHQMD results for d, 3He as well as for the hypernuclei with experimental data.

APA, Harvard, Vancouver, ISO, and other styles

9

WANG, YING, and NORMAN HERRON. "SIZE-DEPENDENT NONRESONANT THIRD-ORDER NONLINEAR SUSCEPTIBILITIES OF CdS CLUSTERS FROM 7 TO 120 Å." Journal of Nonlinear Optical Physics & Materials 01, no. 04 (October 1992): 683–98. http://dx.doi.org/10.1142/s0218199192000339.

Full text

Abstract:

We report the third-order nonlinear susceptibilities χ(3) of CdS clusters (quantum dots) from 7 to 120 Å, measured by third-harmonic generation technique at a fundamental wavelength of 1.91 µm. In the size regime studied, the value of χ(3) first increases with cluster size and then levels off for cluster diameter larger than 60 Å. The volume normalized χ(3) of CdS cluster is about a factor of 2 higher than that of the bulk. These data can be explained by the enhancement in electric field inside the clusters due to the dielectric confinement effect. The size and wavelength dependences of this local field effect have been calculated for CdS clusters. Several trends in the nonresonant χ(3) can be identified: (i) In the absence of quantum confinement effect, the magnitude of χ(3) should be constant in the < 200 Å size regime. It then increases with increasing particle size until the structural resonance regime is reached. (ii) The magnitude of χ(3) can be enhanced by either lowering the refractive index of the surrounding medium or raising the refractive index of the semiconductors. (iii) Quantum confinement, which shifts the band gap to the blue and lowers the refractive index of the semiconductor clusters, reduces the nonresonant χ(3). This is in direct contrast to the resonant nonlinearity which is enhanced by the quantum-confinement effect. Finally, we discuss the size-dependent figure-of-merit of CdS composites for all-optical switching.

APA, Harvard, Vancouver, ISO, and other styles

10

Belousov, A. I., and Yu E. Lozovik. "Quantum melting of mesoscopic clusters." Physics of the Solid State 41, no. 10 (October 1999): 1705–10. http://dx.doi.org/10.1134/1.1131073.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Chakravarty, Charusita. "Structure of Binary Quantum Clusters." Physical Review Letters 75, no. 9 (August 28, 1995): 1727–30. http://dx.doi.org/10.1103/physrevlett.75.1727.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Heidenreich, Andreas, Isidore Last, Uzi Even, and Joshua Jortner. "Nuclear dynamics in quantum clusters." Physical Chemistry Chemical Physics 3, no. 12 (2001): 2325–30. http://dx.doi.org/10.1039/b100550m.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Ramakrishna, M. V., and R. A. Friesner. "Quantum Chemistry of Semiconductor Clusters." Israel Journal of Chemistry 33, no. 1 (1993): 3–8. http://dx.doi.org/10.1002/ijch.199300002.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Kadhim, Bahjat B., Mudar Ahmed Abdulsattar, and Ali Mohammed Ali. "Quantum confinement effects of formation energies and vibrational properties of CdS clusters: A DFT study." International Journal of Modern Physics B 33, no. 16 (June 30, 2019): 1950163. http://dx.doi.org/10.1142/s0217979219501637.

Full text

Abstract:

Formation energies of cadmium sulfide clusters are calculated with the help of density functional theory. The investigated structures include clusters that represent the CdS three main phases, wurtzite, zincblende and rock-salt. The investigation includes electronic, vibrational and thermal properties. CdS clusters are represented by wurtzoids, diamondoids and cuboids for the three phases, wurtzite, zincblende and rock-salt, respectively. The energy gap of the largest investigated molecules approaches that of bulk experimental 2.42 eV. The calculated longitudinal optical (LO) vibrational mode is 304.2 cm[Formula: see text] which is in good agreement with the experimental bulk value of 305 cm[Formula: see text]. To calculate Gibbs free energy, enthalpy and entropy of formation for the clusters, we redefined these quantities so that they represent the difference between the CdS formation energy and their constitutes Cd and S clusters energy. The calculated Gibbs free energy of formation, enthalpy and entropy of the investigated clusters approach that of bulk. Wurtzoids are more stable than diamondoids and cuboids with the release of more heat as deduced from their cluster Gibbs energy and enthalpy of formation. The entropy of clusters is dependent on the size of the cluster. The present method draws a relation between known solid state phases and small cluster calculations.

APA, Harvard, Vancouver, ISO, and other styles

15

Anagnastatos, G. S. "Light mixed alkali microclusters." HNPS Proceedings 3 (December 5, 2019): 154. http://dx.doi.org/10.12681/hnps.2382.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Landman, Uzi, R. N. Barnett, C. L. Cleveland, and Hai-Ping Cheng. "SMALL IS DIFFERENT." International Journal of Modern Physics B 06, no. 23n24 (December 1992): 3623–42. http://dx.doi.org/10.1142/s0217979292001699.

Full text

Abstract:

Investigations of variations of physical and chemical properties of clusters as a function of size allow systematic explorations of evolutionary patterns of materials properties from the molecular scale to the condensed phase regimes. Using classical and quantum molecular dynamics simulations we discuss the dynamics of cluster collisions with surfaces leading to shock formation, dielectrons and sodium solvation in water clusters, size-evolutionary patterns of metallization of sodium-fluoride clusters, and the energetics of metal alloy clusters.

APA, Harvard, Vancouver, ISO, and other styles

17

Pedone, Ignazio, and Antonio Lioy. "Quantum Key Distribution in Kubernetes Clusters." Future Internet 14, no. 6 (May 25, 2022): 160. http://dx.doi.org/10.3390/fi14060160.

Full text

Abstract:

Quantum Key Distribution (QKD) represents a reasonable countermeasure to the advent of Quantum Computing and its impact on current public-key cryptography. So far, considerable efforts have been devoted to investigate possible application scenarios for QKD in several domains such as Cloud Computing and NFV. This paper extends a previous work whose main objective was to propose a new software stack, the Quantum Software Stack (QSS), to integrate QKD into software-defined infrastructures. The contribution of this paper is twofold: enhancing the previous work adding functionalities to the first version of the QSS, and presenting a practical integration of the QSS in Kubernetes, which is the de-facto standard for container orchestration.

APA, Harvard, Vancouver, ISO, and other styles

18

KAPLAN, I. G., R. SANTAMARÍA, and O. NOVARO. "SIZE EFFECTS AND THE ROLE OF NONADDITIVE FORCES IN NEUTRAL AND ANIONIC SILVER-CLUSTER STABILITY." Surface Review and Letters 03, no. 01 (February 1996): 235–39. http://dx.doi.org/10.1142/s0218625x96000462.

Full text

Abstract:

The precise quantum-chemical study of neutral and anionic silver clusters manifests the pronounced size effect for the vertical ionization potential (VIP), vertical detachment energy (VDE), and atomic detachment energy (ε1). The additive and nonadditive contributions to the binding energy of clusters are calculated and their role in the cluster stability is discussed.

APA, Harvard, Vancouver, ISO, and other styles

19

Han, Zhen, Xi-Yan Dong, Peng Luo, Si Li, Zhao-Yang Wang, Shuang-Quan Zang, and Thomas C. W. Mak. "Ultrastable atomically precise chiral silver clusters with more than 95% quantum efficiency." Science Advances 6, no. 6 (February 2020): eaay0107. http://dx.doi.org/10.1126/sciadv.aay0107.

Full text

Abstract:

Monolayer-protected atomically precise silver clusters display low photoluminescence (PL) quantum yield (QY) and susceptibility under ambient conditions, and their chiroptical activities also remain underdeveloped. Here, we report enantiomers of an octahedral Ag6 cluster prepared via one-step synthesis using designed chiral ligands at ambient temperature. These clusters exhibit a highest PLQY (300 K) >95.0% and retain their structural integrity and emission up to 150°C in air. Atomically precise structural determination combined with photophysical and computational analysis revealed that thermally activated delayed fluorescence, observed in silver cluster systems, is responsible for the high PLQY, which combines chirality in excited states to generate strong circularly polarized luminescence. These unprecedented findings open up horizons of investigation of monolayer-protected silver clusters for future luminescence applications.

APA, Harvard, Vancouver, ISO, and other styles

20

Cesca, Tiziana, Boris Kalinic, Chiara Maurizio, Niccolò Michieli, Carlo Scian, and Giovanni Mattei. "Amplified sensitization of Er3+ luminescence in silica by AuN quantum clusters upon annealing in a reducing atmosphere." RSC Advances 6, no. 101 (2016): 99376–84. http://dx.doi.org/10.1039/c6ra16931g.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

RÖPKE, GERD. "LIGHT CLUSTERS IN NUCLEAR MATTER." International Journal of Modern Physics E 20, no. 04 (April 2011): 897–901. http://dx.doi.org/10.1142/s0218301311018927.

Full text

Abstract:

Within a quantum statistical approach, a in-medium Schrödinger equation is derived for a few-nucleon system embedded in nuclear matter. Medium modifications of the cluster quasiparticles are described by self-energy and Pauli blocking effects. Benchmarks such as the nuclear statistical equilibrium, virial expansion and the relativistic mean field approximation are considered. An interesting effect is the formation of a four- or two-nucleon quantum condensate, showing the crossover from Cooper pairing to Bose-Einstein condensation. The resulting thermodynamic properties are of interest for heavy-ion collisions and astrophysical applications. Quantum condensates and the Mott effect are also of relevance for the structure of finite nuclei, specially dilute excited states like the Hoyle state of 12 C .

APA, Harvard, Vancouver, ISO, and other styles

22

Oleshko, Vladimir P., Peter A. Crozier, Nick Schryvers, and Michail Vargaftik. "Mesostructure Of Pd And Pt Nanoclusters Chemically Stabilized With Phosphide And Phenanthroline Ligands: Hrtem And Aem Characterization." Microscopy and Microanalysis 5, S2 (August 1999): 184–85. http://dx.doi.org/10.1017/s1431927600014240.

Full text

Abstract:

The noble metal (Me = Au, Pd, Rh, and Pt) polynuclear coordination compounds of Chini’s type eventually serve as a remarkable bridge between molecular clusters and metal colloids. The sizes of the metal cores of the cluster compounds are close to lower sizes of colloidal metal particles. However, chemically stabilized nanoclusters have a distinct ligand environment with a definite stoichiometry inherent to molecular clusters. Interest in structures of the cluster compounds has increased in recent years in view of their unique selective catalytic properties under mild conditions, which, in principle, open a way to the development of a new branch of catalysis by metal clusters, quantum-size effects in the thermodynamic properties, and applications as nano-sized electronic devices (quantum dots). A key feature in structural characterization of such species (they are amorphous solids usually unsuitable for x-ray diffraction analysis) is to understand the relations between the atomic arrangement, electronic structure and chemical reactivity.

APA, Harvard, Vancouver, ISO, and other styles

23

Bawendi, M. G., M. L. Steigerwald, and L. E. Brus. "The Quantum Mechanics of Larger Semiconductor Clusters ("Quantum Dots")." Annual Review of Physical Chemistry 41, no. 1 (October 1990): 477–96. http://dx.doi.org/10.1146/annurev.pc.41.100190.002401.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Xie, Mingchen, Chunmiao Han, Qianqian Liang, Jing Zhang, Guohua Xie, and Hui Xu. "Highly efficient sky blue electroluminescence from ligand-activated copper iodide clusters: Overcoming the limitations of cluster light-emitting diodes." Science Advances 5, no. 6 (June 2019): eaav9857. http://dx.doi.org/10.1126/sciadv.aav9857.

Full text

Abstract:

Organic light-emitting diodes using cluster emitters have recently emerged as a flexible optoelectronic platform to extend their biological and optical applications. However, their inefficient cluster-centered excited states and deficient electrical properties limit device performance. Here, we introduce donor groups in organic ligands to form ligand-activated clusters, enabling the fabrication of the first cluster-based sky blue–emitting device with a record 30- and 8-fold increased luminance and external quantum efficiency up to ~7000 nits and ~8%, respectively. We show that the electron-donating effect of donor groups can enhance ligand-centered transitions and thoroughly eliminate cluster-centered excited states by delocalizing the molecular transition orbitals from the cluster unit to the ligand, leading to 13-fold increased photoluminescence quantum yield. In turn, the excellent rigidity and photostability of the cluster unit improve the color purity and efficiency stability of the devices. These results will motivate the further development of high-performance optoelectronic clusters by ligand engineering.

APA, Harvard, Vancouver, ISO, and other styles

25

Anagnostatos, G. S. "Clusters in Atoms and Nuclei." HNPS Proceedings 1 (February 18, 2020): 98. http://dx.doi.org/10.12681/hnps.2829.

Full text

Abstract:

Small aggregates of particles, possessing different properties than those in bulk (i.e., in crystals or in nuclear matter), are reviewed here. Specifically, while some categories of atomic clusters (regular or bosonic) are in a solid state of matter and their structure possesses, more or less, definite geometric picture of packing of spheres standing for atoms, some other categories of atomic clusters (quantum or fermionic) are in a liquid (or gas) state of matter and their structure follows quantum mechanics whose only the average forms have a geometrical representation. These quantum clusters can be extended to include nucléon clusters of spheres standing for the nucléon bags with rather impressive results. All families of clusters considered together could be seen as a fifth state of matter.

APA, Harvard, Vancouver, ISO, and other styles

26

McGrath, M. J., T. Olenius, I. K. Ortega, V. Loukonen, P. Paasonen, T. Kurtén, M. Kulmala, and H. Vehkamäki. "Atmospheric Cluster Dynamics Code: a flexible method for solution of the birth-death equations." Atmospheric Chemistry and Physics Discussions 11, no. 9 (September 9, 2011): 25263–95. http://dx.doi.org/10.5194/acpd-11-25263-2011.

Full text

Abstract:

Abstract. The Atmospheric Cluster Dynamics Code (ACDC) is presented and explored. This program was created to study the first steps of atmospheric new particle formation by examining the formation of molecular clusters from atmospherically relevant molecules. The program models the cluster kinetics by explicit solution of the birth–death equations, using an efficient computer script for their generation and the MATLAB ode15s routine for their solution. Through the use of evaporation rate coefficients derived from formation free energies calculated by quantum chemical methods for clusters containing dimethylamine or ammonia and sulphuric acid, we have explored the effect of changing various parameters at atmospherically relevant monomer concentrations. We have included in our model clusters with 0–4 base molecules and 0–4 sulfuric acid molecules for which we have commensurable quantum chemical data. The tests demonstrate that large effects can be seen for even small changes in different parameters, due to the non-linearity of the system. In particular, the temperature and sticking probabilities both have a large impact on all clusters, while the boundary effects (allowing clusters to grow to sizes beyond the largest cluster that the code keeps track of, or forbidding such processes), coagulation sink terms, non-monomer collisions, and monomer concentrations can all have significant effects. Removal of coagulation sink terms prevented the system from reaching the steady state when all the initial cluster concentrations were set to the default value of 1 m−3, which is probably an effect caused by studying only relatively small cluster sizes.

APA, Harvard, Vancouver, ISO, and other styles

27

McGrath, M. J., T. Olenius, I. K. Ortega, V. Loukonen, P. Paasonen, T. Kurtén, M. Kulmala, and H. Vehkamäki. "Atmospheric Cluster Dynamics Code: a flexible method for solution of the birth-death equations." Atmospheric Chemistry and Physics 12, no. 5 (March 2, 2012): 2345–55. http://dx.doi.org/10.5194/acp-12-2345-2012.

Full text

Abstract:

Abstract. The Atmospheric Cluster Dynamics Code (ACDC) is presented and explored. This program was created to study the first steps of atmospheric new particle formation by examining the formation of molecular clusters from atmospherically relevant molecules. The program models the cluster kinetics by explicit solution of the birth–death equations, using an efficient computer script for their generation and the MATLAB ode15s routine for their solution. Through the use of evaporation rate coefficients derived from formation free energies calculated by quantum chemical methods for clusters containing dimethylamine or ammonia and sulphuric acid, we have explored the effect of changing various parameters at atmospherically relevant monomer concentrations. We have included in our model clusters with 0–4 base molecules and 0–4 sulfuric acid molecules for which we have commensurable quantum chemical data. The tests demonstrate that large effects can be seen for even small changes in different parameters, due to the non-linearity of the system. In particular, changing the temperature had a significant impact on the steady-state concentrations of all clusters, while the boundary effects (allowing clusters to grow to sizes beyond the largest cluster that the code keeps track of, or forbidding such processes), coagulation sink terms, non-monomer collisions, sticking probabilities and monomer concentrations did not show as large effects under the conditions studied. Removal of coagulation sink terms prevented the system from reaching the steady state when all the initial cluster concentrations were set to the default value of 1 m−3, which is probably an effect caused by studying only relatively small cluster sizes.

APA, Harvard, Vancouver, ISO, and other styles

28

Shi, Benjamin X., Venkat Kapil, Andrea Zen, Ji Chen, Ali Alavi, and Angelos Michaelides. "General embedded cluster protocol for accurate modeling of oxygen vacancies in metal-oxides." Journal of Chemical Physics 156, no. 12 (March 28, 2022): 124704. http://dx.doi.org/10.1063/5.0087031.

Full text

Abstract:

The O vacancy (Ov) formation energy, EOv, is an important property of a metal-oxide, governing its performance in applications such as fuel cells or heterogeneous catalysis. These defects are routinely studied with density functional theory (DFT). However, it is well-recognized that standard DFT formulations (e.g., the generalized gradient approximation) are insufficient for modeling the Ov, requiring higher levels of theory. The embedded cluster method offers a promising approach to compute EOv accurately, giving access to all electronic structure methods. Central to this approach is the construction of quantum(-mechanically treated) clusters placed within suitable embedding environments. Unfortunately, current approaches to constructing the quantum clusters either require large system sizes, preventing application of high-level methods, or require significant manual input, preventing investigations of multiple systems simultaneously. In this work, we present a systematic and general quantum cluster design protocol that can determine small converged quantum clusters for studying the Ov in metal-oxides with accurate methods, such as local coupled cluster with single, double, and perturbative triple excitations. We apply this protocol to study the Ov in the bulk and surface planes of rutile TiO2 and rock salt MgO, producing the first accurate and well-converged determinations of EOv with this method. These reference values are used to benchmark exchange–correlation functionals in DFT, and we find that all the studied functionals underestimate EOv, with the average error decreasing along the rungs of Jacob’s ladder. This protocol is automatable for high-throughput calculations and can be generalized to study other point defects or adsorbates.

APA, Harvard, Vancouver, ISO, and other styles

29

Shigeta, Yasuteru, Hidemi Nagao, Yasunori Yoshioka, and Kizashi Yamaguchi. "Theoretical Studies on Quantum Tunneling of Spins in Cluster of Clusters." Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals 342, no. 1 (May 1, 2000): 279–84. http://dx.doi.org/10.1080/10587250008038278.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Shrivastava, Keshav N. "Quantum Hall Effect in AlGaAs and Graphite Quantum Dots." Advanced Materials Research 667 (March 2013): 1–9. http://dx.doi.org/10.4028/www.scientific.net/amr.667.1.

Full text

Abstract:

Abstract. The 30 nm wide quantum wells on a 4x4 mm2 piece of GaAs/AlGaAs are formed when the layers of GaAs are deposited on AlGaAs films. The two-dimensional density of electrons is 3x1011 cm-2 and the mobility is 32x106 cm2/Vs. In such a sample the Hall resistivity as a function of magnetic field is not a linear function. Hence a suitable theory to understand the Hall effect is formulated. We find that there are phase transitions as a function of temperature. There are lots of fractions of charge which are explained on the basis of spin and orbital angular momentum of the electron. The nano meter size films of graphite also show that the Hall resistivity is non-linear and shows steps as a function of magnetic field. We make an effort to understand the steps in the Hall effect resistivity of graphite with quantum wells formed on the surface. It is found that the fractions are in four categories, (i) the principal fractions which are determined by spin and orbital angular momenta, (ii) the resonances which occur at the difference between two values such as =1-2, (iii) two-particle states which occur at the sum of the two frequencies and (iv) there are clusters of electrons localized in some areas of the sample. The spin in the clusters is polarized so that it becomes NS which is not 1/2 but depends on the number N, of electrons in a cluster.

APA, Harvard, Vancouver, ISO, and other styles

31

Fel'dman, E. B., A. N. Pyrkov, and A. I. Zenchuk. "Solid-state multiple quantum NMR in quantum information processing: exactly solvable models." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, no. 1976 (October 13, 2012): 4690–712. http://dx.doi.org/10.1098/rsta.2011.0499.

Full text

Abstract:

Multiple quantum (MQ) NMR is an effective tool for the generation of a large cluster of correlated particles, which, in turn, represent a basis for quantum information processing devices. Studying the available exactly solvable models clarifies many aspects of the quantum information. In this study, we consider two exactly solvable models in the MQ NMR experiment: (i) the isolated system of two spin- particles (dimers) and (ii) the large system of equivalent spin- particles in a nanopore. The former model is used to describe the quantum correlations and their relations with the MQ NMR coherences, whereas the latter helps one to model the creation and decay of large clusters of correlated particles.

APA, Harvard, Vancouver, ISO, and other styles

32

Wang, Jian Guang, and Peter Kroll. "Structural, Electronic and Optical Properties of SiC Quantum Dots." Journal of Nano Research 18-19 (July 2012): 77–87. http://dx.doi.org/10.4028/www.scientific.net/jnanor.18-19.77.

Full text

Abstract:

We Perform Density Functional Theory Calculations of the Hydrogen-Passivated Topological Silicon Carbide Quantum Dots (QDs) and Investigate their Structural, Electronic and Optical Properties. We Study Clusters Constructed from 3C-Sic with up to 8 Topological Shells, Corresponding to Diameters up to 2.2 Nm, Terminated Homogeneously with either Si-H or C-H Bonds. All Qds Exhibit Tensile Strain (1-5 %) within the Cluster Core. the Larger the Cluster, the Smaller the Strain in the Interior, however. Tensile Strain Increases from the inside of the Cluster towards the outside, Reaches a Maximum at the Second Layer below the Surface, and Vanishes only for Bonds Involving Surface Si or C Atoms. Quantum-Confinement Effects Are Observed for the Energy Gaps and Optical Gaps of SiC QDs. Size Has a Major Impact on the Absorption Edge in Comparison to a Weak Effect on the Photon Energy of the Spectra Maxima. Our Calculations Show that Surface Termination Plays a Crucial Role and Strongly Affects Energy Gaps, Optical Gaps and Optical Spectra. Orbitals around the HOMO-LUMO Gap Predominantly Localize within the Core of the Cluster, with Significant Contributions by the Surface for Si-H Terminated Clusters only.

APA, Harvard, Vancouver, ISO, and other styles

33

Meuwly, Markus. "Quantum Simulations of Nen−OH+Clusters." Journal of Physical Chemistry A 104, no. 30 (August 2000): 7144–50. http://dx.doi.org/10.1021/jp001380d.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Muhammed, M. A. Habeeb, Ajay Kumar Shaw, Samir Kumar Pal, and T. Pradeep. "Quantum Clusters of Gold Exhibiting FRET." Journal of Physical Chemistry C 112, no. 37 (August 21, 2008): 14324–30. http://dx.doi.org/10.1021/jp804597r.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Mercier, B., G. Ledoux, C. Dujardin, D. Nicolas, B. Masenelli, P. Mélinon, and G. Bergeret. "Quantum confinement effect on Gd2O3 clusters." Journal of Chemical Physics 126, no. 4 (January 28, 2007): 044507. http://dx.doi.org/10.1063/1.2431366.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Alivisatos, A. P. "Semiconductor Clusters, Nanocrystals, and Quantum Dots." Science 271, no. 5251 (February 16, 1996): 933–37. http://dx.doi.org/10.1126/science.271.5251.933.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Benoit, David M., and David C. Clary. "Quantum Simulation of Phenol−Water Clusters." Journal of Physical Chemistry A 104, no. 23 (June 2000): 5590–99. http://dx.doi.org/10.1021/jp994420q.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Gadre, Shridhar R., Sachin D. Yeole, and Nityananda Sahu. "Quantum Chemical Investigations on Molecular Clusters." Chemical Reviews 114, no. 24 (October 24, 2014): 12132–73. http://dx.doi.org/10.1021/cr4006632.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Gai, Huadong, Liem X. Dang, Gregory K. Schenter, and Bruce C. Garrett. "Quantum Simulation of Aqueous Ionic Clusters." Journal of Physical Chemistry 99, no. 36 (September 1995): 13303–6. http://dx.doi.org/10.1021/j100036a001.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Affronte, M., F. Troiani, A. Ghirri, S. Carretta, P. Santini, R. Schuecker, G. Timco, and R. E. P. Winpenny. "Molecular spin clusters for quantum computation." Journal of Magnetism and Magnetic Materials 310, no. 2 (March 2007): e501-e502. http://dx.doi.org/10.1016/j.jmmm.2006.10.622.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Rama Krishna, M. V., and R. A. Friesner. "Quantum confinement effects in semiconductor clusters." Journal of Chemical Physics 95, no. 11 (December 1991): 8309–22. http://dx.doi.org/10.1063/1.461258.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Raghu, C., Indranil Rudra, Diptiman Sen, and S. Ramasesha. "Quantum phenomena in magnetic nano clusters." Journal of Chemical Sciences 113, no. 5-6 (October 2001): 459–86. http://dx.doi.org/10.1007/bf02708784.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

Filinov, A. V., M. Bonitz, and Yu E. Lozovik. "Excitonic clusters in coupled quantum dots." Journal of Physics A: Mathematical and General 36, no. 22 (May 23, 2003): 5899–904. http://dx.doi.org/10.1088/0305-4470/36/22/310.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Whaley, K. Birgitta. "Structure and dynamics of quantum clusters." International Reviews in Physical Chemistry 13, no. 1 (March 1994): 41–84. http://dx.doi.org/10.1080/01442359409353290.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Stringari, S. "Quantum statistical effects in helium clusters." Zeitschrift f�r Physik D Atoms, Molecules and Clusters 20, no. 1-4 (March 1991): 219–22. http://dx.doi.org/10.1007/bf01543977.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Kupiainen, O., I. K. Ortega, T. Kurtén, and H. Vehkamäki. "Amine substitution into sulfuric acid – ammonia clusters." Atmospheric Chemistry and Physics Discussions 11, no. 11 (November 18, 2011): 30853–75. http://dx.doi.org/10.5194/acpd-11-30853-2011.

Full text

Abstract:

Abstract. The substitution of ammonia by dimethylamine in sulfuric acid – ammonia – dimethylamine clusters was studied using a collision and evaporation dynamics model. Quantum chemical formation free energies were computed using B3LYP/CBSB7 for geometries and frequencies and RI-CC2/aug-cc-pV(T+d)Z for electronic energies. We first demonstrate the good performance of our method by a comparison with an experimental study investigating base substitution in positively charged clusters, and then continue by simulating base exchange in neutral clusters, which cannot be measured directly. Collisions of a dimethylamine molecule with an ammonia containing positively charged cluster result in the instantaneous evaporation of an ammonia molecule, while the dimethylamine molecule remains in the cluster. According to our simulations, a similar base exchange can take place in neutral clusters, although the overall process is more complicated. Neutral sulfuric acid – ammonia clusters are significantly less stable than their positively charged counterparts, resulting in a competition between cluster evaporation and base exchange.

APA, Harvard, Vancouver, ISO, and other styles

47

Kupiainen, O., I. K. Ortega, T. Kurtén, and H. Vehkamäki. "Amine substitution into sulfuric acid – ammonia clusters." Atmospheric Chemistry and Physics 12, no. 8 (April 16, 2012): 3591–99. http://dx.doi.org/10.5194/acp-12-3591-2012.

Full text

Abstract:

Abstract. The substitution of ammonia by dimethylamine in sulfuric acid – ammonia – dimethylamine clusters was studied using a collision and evaporation dynamics model. Quantum chemical formation free energies were computed using B3LYP/CBSB7 for geometries and frequencies and RI-CC2/aug-cc-pV(T+d)Z for electronic energies. We first demonstrate the good performance of our method by a comparison with an experimental study investigating base substitution in positively charged clusters, and then continue by simulating base exchange in neutral clusters, which cannot be measured directly. Collisions of a dimethylamine molecule with an ammonia containing positively charged cluster result in the instantaneous evaporation of an ammonia molecule, while the dimethylamine molecule remains in the cluster. According to our simulations, a similar base exchange can take place in neutral clusters, although the overall process is more complicated. Neutral sulfuric acid – ammonia clusters are significantly less stable than their positively charged counterparts, resulting in a competition between cluster evaporation and base exchange.

APA, Harvard, Vancouver, ISO, and other styles

48

RAMA KRISHNA, M. V., and K. B. WHALEY. "STRUCTURE AND EXCITATIONS OF QUANTUM LIQUID CLUSTERS." Modern Physics Letters B 04, no. 14 (August 10, 1990): 895–904. http://dx.doi.org/10.1142/s0217984990001100.

Full text

Abstract:

We review recent theoretical progress in the evaluation of collective excitation spectra of quantum liquid clusters, with specific application to 4 He N. An excitation operator theory together with the variational Monte Carlo method has provided a powerful means of calculating the excited state wavefunctions and energies. The compressional excitations of 4 He N clusters calculated from the excitation operator theory agree well with the results of a quantum liquid drop theory based on accurate knowledge of microscopic density correlations in the ground state. The compressional excitation spectra evolve toward the spectrum of bulk He II as N increases, with the roton structure first appearing at N≈70. The implication for the finite size scaling of superfluid behavior in these clusters is discussed. These techniques now allow microscopic study of clusters containing foreign species, and can also be extended to quantum solid clusters.

APA, Harvard, Vancouver, ISO, and other styles

49

Siu, Timothy C., Joshua Y. Wong, Matthew O. Hight, and Timothy A. Su. "Single-cluster electronics." Physical Chemistry Chemical Physics 23, no. 16 (2021): 9643–59. http://dx.doi.org/10.1039/d1cp00809a.

Full text

Abstract:

This article reviews the scope of inorganic cluster compounds measured in single-molecule junctions. The article explores how the structure and bonding of inorganic clusters give rise to specific quantum transport phenomena in molecular junctions.

APA, Harvard, Vancouver, ISO, and other styles

50

Jiang, Hao, Oskar K. G. Svensson, and Ulf Ryde. "Quantum Mechanical Calculations of Redox Potentials of the Metal Clusters in Nitrogenase." Molecules 28, no. 1 (December 21, 2022): 65. http://dx.doi.org/10.3390/molecules28010065.

Full text

Abstract:

We have calculated redox potentials of the two metal clusters in Mo-nitrogenase with quantum mechanical (QM) calculations. We employ an approach calibrated for iron–sulfur clusters with 1–4 Fe ions, involving QM-cluster calculations in continuum solvent and large QM systems (400–500 atoms), based on structures from combined QM and molecular mechanics (QM/MM) geometry optimisations. Calculations on the P-cluster show that we can reproduce the experimental redox potentials within 0.33 V. This is similar to the accuracy obtained for the smaller clusters, although two of the redox reactions involve also proton transfer. The calculated P1+/PN redox potential is nearly the same independently of whether P1+ is protonated or deprotonated, explaining why redox titrations do not show any pH dependence. For the FeMo cluster, the calculations clearly show that the formal oxidation state of the cluster in the resting E0 state is , in agreement with previous experimental studies and QM calculations. Moreover, the redox potentials of the first five E0–E4 states are nearly constant, as is expected if the electrons are delivered by the same site (the P-cluster). However, the redox potentials are insensitive to the formal oxidation states of the Fe ion (i.e., whether the added protons bind to sulfide or Fe ions). Finally, we show that the later (E4–E8) states of the reaction mechanism have redox potential that are more positive (i.e., more exothermic) than that of the E0/E1 couple.

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!