Structure and Growth of Small Palladium Clusters

1992 ◽  
Vol 291 ◽  
Author(s):  
Y. S. Li ◽  
Y. Cai ◽  
J. M. Newsam
Keyword(s):  
Nearest Neighbor ◽  
Magic Number ◽  
High Symmetry ◽  
Many Body ◽  
Slow Convergence ◽  
Palladium Clusters ◽  
Equilibrium Structures ◽  
The Many ◽  
Cohesive Energies ◽  
Nearest Neighbor Distances

ABSTRACTWe study the structure and growth sequence of small palladium clusters Pdn using the Many-Body Alloy (MBA) potential and simulated annealing techniques. Our results show the preference of compact polyhedral structures. These equilibrium structures are compared with the bulk Pd crystal in terms of cohesive energies and nearest neighbor distances. Both the cohesive energy and the nearest neighbor distance show a slow convergence to bulk behaviors. By analyzing the detailed structures and cohesive energies, we find that Pd4, Pd7 and Pd13 are magic number structures, which are the consequence of their high symmetry and large coordination number.

scholarly journals Using Matrix-Product States for Open Quantum Many-Body Systems: Efficient Algorithms for Markovian and Non-Markovian Time-Evolution

Entropy ◽  
2020 ◽  
Vol 22 (9) ◽  
pp. 984
Author(s):  
Regina Finsterhölzl ◽  
Manuel Katzer ◽  
Andreas Knorr ◽  
Alexander Carmele
Keyword(s):  
Time Evolution ◽  
Nearest Neighbor ◽  
Matrix Product ◽  
Body System ◽  
Many Body ◽  
Initial State ◽  
Matrix Product States ◽  
Open Quantum ◽  
Many Body Systems ◽  
The Many

This paper presents an efficient algorithm for the time evolution of open quantum many-body systems using matrix-product states (MPS) proposing a convenient structure of the MPS-architecture, which exploits the initial state of system and reservoir. By doing so, numerically expensive re-ordering protocols are circumvented. It is applicable to systems with a Markovian type of interaction, where only the present state of the reservoir needs to be taken into account. Its adaption to a non-Markovian type of interaction between the many-body system and the reservoir is demonstrated, where the information backflow from the reservoir needs to be included in the computation. Also, the derivation of the basis in the quantum stochastic Schrödinger picture is shown. As a paradigmatic model, the Heisenberg spin chain with nearest-neighbor interaction is used. It is demonstrated that the algorithm allows for the access of large systems sizes. As an example for a non-Markovian type of interaction, the generation of highly unusual steady states in the many-body system with coherent feedback control is demonstrated for a chain length of N=30.

Role of the second nearest-neighbor hoppings in a disordered Bose–Hubbard Hamiltonian in the Many-Body Localization

2020 ◽  
Vol 93 (9) ◽  
Author(s):  
Edith Djoukouo Ngueyounou ◽  
Kanabet Yapara ◽  
Celsus Bouri ◽  
Hugues Merlain Tetchou Nganso ◽  
Moïse Godfroy Kwato Njock
Keyword(s):  
Nearest Neighbor ◽  
Many Body ◽  
Hubbard Hamiltonian ◽  
The Many

A Full Additive QM/MM Scheme for the Computation of Molecular Crystals with Extension to Many-Body Expansions

2018 ◽  
Author(s):  
Thorsten Teuteberg ◽  
Marco Eckhoff ◽  
Ricardo A. Mata
Keyword(s):  
Single Molecule ◽  
Molecular Crystals ◽  
Lattice Energy ◽  
Molecular Geometry ◽  
Many Body ◽  
Cell Parameters ◽  
Straightforward Application ◽  
The Many ◽  
The One ◽  
Cohesive Energies

An additive quantum mechanics/molecular mechanics (QM/MM) model for the theoretical investigation of molecular crystals (AC-QM/MM) is presented. At the one-body level, a single molecule is chosen as the QM region. The MM region around it consists of a finite cluster of explicit MM atoms, represented by point charges and Lennard-Jones potentials, with additional background charges to mimic periodic electrostatics. Cluster charges are QM-derived and calculated self-consistently to ensure a polarizable embedding. We have also considered the extension to many-body QM corrections, calculating the interactions of a central molecule to neighbouring units in the crystal. Full gradient expressions have been derived, also including symmetry information. The scheme allows for the calculation of molecular properties as well as unconstrained optimisations of the molecular geometry and cell parameters with respect to the lattice energy. Benchmarking the approach with the X23 reference set confirms the convergence pattern of the many-body extension, although comparison to plane wave DFT reveals a systematic overestimation of cohesive energies by 6-16 kJ·mol<sup>−1</sup> . While the scheme primarily aims to provide an inexpensive and flexible way to model a molecule in a crystal environment, it can also be used to reach highly accurate cohesive energies by the straightforward application of wave function correlated approaches. Calculations with local coupled cluster with singles, doubles, and perturbative triples, albeit limited to numerical gradients, show an impressive agreement with experimental estimates for small molecular crystals.<br><br>

A Full Additive QM/MM Scheme for the Computation of Molecular Crystals with Extension to Many-Body Expansions

2018 ◽  
Author(s):  
Thorsten Teuteberg ◽  
Marco Eckhoff ◽  
Ricardo A. Mata
Keyword(s):  
Single Molecule ◽  
Molecular Crystals ◽  
Lattice Energy ◽  
Molecular Geometry ◽  
Many Body ◽  
Cell Parameters ◽  
Straightforward Application ◽  
The Many ◽  
The One ◽  
Cohesive Energies

An additive quantum mechanics/molecular mechanics (QM/MM) model for the theoretical investigation of molecular crystals (AC-QM/MM) is presented. At the one-body level, a single molecule is chosen as the QM region. The MM region around it consists of a finite cluster of explicit MM atoms, represented by point charges and Lennard-Jones potentials, with additional background charges to mimic periodic electrostatics. Cluster charges are QM-derived and calculated self-consistently to ensure a polarizable embedding. We have also considered the extension to many-body QM corrections, calculating the interactions of a central molecule to neighbouring units in the crystal. Full gradient expressions have been derived, also including symmetry information. The scheme allows for the calculation of molecular properties as well as unconstrained optimisations of the molecular geometry and cell parameters with respect to the lattice energy. Benchmarking the approach with the X23 reference set confirms the convergence pattern of the many-body extension, although comparison to plane wave DFT reveals a systematic overestimation of cohesive energies by 6-16 kJ·mol<sup>−1</sup> . While the scheme primarily aims to provide an inexpensive and flexible way to model a molecule in a crystal environment, it can also be used to reach highly accurate cohesive energies by the straightforward application of wave function correlated approaches. Calculations with local coupled cluster with singles, doubles, and perturbative triples, albeit limited to numerical gradients, show an impressive agreement with experimental estimates for small molecular crystals.<br><br>

Asymmetrical Elementary Excitations Responsible for the Ferrimagnetism in an Antiferromagnetic Spin-1/2 Zigzag Ladder

2013 ◽  
Vol 380-384 ◽  
pp. 4262-4267
Author(s):  
Zhong Long Wang ◽  
Qiao Wu ◽  
Lin Jie Ding
Keyword(s):  
Random Phase Approximation ◽  
Nearest Neighbor ◽  
Random Phase ◽  
Exchange Interactions ◽  
Many Body ◽  
Elementary Excitations ◽  
Greens Function ◽  
The Many ◽  
Antiferromagnetic Spin ◽  
Ferrimagnetic Ordering

The finite-temperature magnetic properties of an antiferromagnetic (AF) bond alternating S=1/2 zigzag spin chain with asymmetrical AF next-nearest-neighbor (NNN) exchange interactions in an external magnetic field are investigated by means of the many-body Greens function theory within random phase approximation. The results show that when the NNN exchange interactions are asymmetrical, the spin system exhibit a clear ferrimagnetic ordering at finite temperatures. It is shown that the ferrimagnetic behavior is attributed to asymmetrical elementary excitations, resulting from the competition between the spin frustrations and magnetic excitations reduced by the asymmetrical NNN interactions. The mechanism of this ferrimagnetism is much different from a common one which originates from mixed spins with different spin values through antiparallel spin alignments.

Application of Lattice Imaging Techniques to Amorphous Films

1975 ◽  
Vol 33 ◽  
pp. 8-9
Author(s):  
S. R. Herd ◽  
P. Chaudhari
Keyword(s):  
Nearest Neighbor ◽  
Random Network ◽  
Imaging Techniques ◽  
Network Models ◽  
Accurate Method ◽  
Direct Transmission ◽  
Lattice Imaging ◽  
Transmission Electron ◽  
Lattice Planes ◽  
Nearest Neighbor Distances

Electron diffraction and direct transmission have been used extensively to study the local atomic arrangement in amorphous solids and in particular Ge. Nearest neighbor distances had been calculated from E.D. profiles and the results have been interpreted in terms of the microcrystalline or the random network models. Direct transmission electron microscopy appears the most direct and accurate method to resolve this issue since the spacial resolution of the better instruments are of the order of 3Å. In particular the tilted beam interference method is used regularly to show fringes corresponding to 1.5 to 3Å lattice planes in crystals as resolution tests.

On the many-body theory of nuclear reactions

1968 ◽  
Vol 111 (1) ◽  
pp. 392-416 ◽  
Author(s):  
K DIETRICH ◽  
K HARA
Keyword(s):  
Nuclear Reactions ◽  
Many Body ◽  
Many Body Theory ◽  
The Many ◽  
Body Theory
Sign in / Sign up

Export Citation Format

Share Document