Search results for "force field"
showing 10 items of 55 documents
Interpretation of EXAFS in ReO3using molecular dynamics simulations
2009
Temperature dependent Re L3-edge EXAFS signals from perovskite-type cubic ReO3 have been successfully interpreted using a combination of classical NVT molecular dynamics (MD) and ab initio multiple-scattering approach. The force field model, required for MD simulations, has been determined by fitting the Re-O and O-O pairwise interatomic potentials to a set of experimental data (lattice parameter, elastic constants and bulk modulus) and phonon frequencies, theoretically calculated from the first principles at high symmetry points of the Brillouin zone. The MD simulations reproduce well the anisotropy of thermal vibration for oxygen atoms and confirm a deviation of the mean Re-O-Re angle fro…
Regional Susceptibility in VCD Spectra to Dynamic Molecular Motions
2018
Experimental and theoretical studies of the vibrational circular dichroism (VCD) spectrum of 3-methyl-1-(methyldiphenlsilyl)-1-phenylbutan-1-ol, whose absolute configuration is key to elucidating the Brook rearrangement of tertiary benzylic α-hydroxylsilanes, are presented. It is found that the entire OH-bending region in this spectrum—a region that provides important marker bands—cannot be reproduced at all by standard theoretical approaches even though other regions are well described. Using a novel approach to disentangle contributions to the rotational strength of these bands, internal coordinates are identified that critically influence the appearance of this part of the spectrum. We s…
The equilibrium structure of propadienylidene
1999
Abstract A coupled-cluster study of the equilibrium geometry of propadienylidene (C3H2) is presented. Deviations between a recently reported experimental re structure and those computed at the CCSD(T)/cc-pVQZ and CCSD(T)/cc-pCVQZ levels are larger than expected. A closer analysis reveals that this discrepancy is due to inaccuracies in the cubic force field that was used to correct the measured rotational constants for vibrational effects. A satisfactory agreement between theory and experiment is obtained if the vibrational effects on the rotational constants are computed from harmonic and cubic force fields determined at either the CCSD(T)/cc-pVTZ and CCSD(T)/cc-pCVTZ levels. Revised values…
Piezoelectric coefficients by molecular dynamics simulations in the constant stress ensemble: A case study of quartz
2006
Piezoelectric (strain) coefficients dij of quartz are calculated in terms of molecular dynamics as a function of pressure and temperature. We review the necessary formulas for the computation of electromechanical materials coefficients obtained at constant stress and temperature, and discuss how to overcome complications of the definition of polarization variations due to fluctuating box geometries. A method is employed suppressing significantly stochastic fluctuations of the estimators for piezoelectric coefficients. A recently suggested force field for the simulation of SiO2 reproduces available experimental data quite accurately. Predictions are made for the pressure dependence of dij of…
Simulation of Young’s moduli for hexagonal ZnO [0 0 0 1]-oriented nanowires: first principles and molecular mechanical calculations
2017
The authors thank A Gulans, B Polyakov and S Vlassov for stimulating discussions. This study has been supported by the ERA.Net RUS Plus project No. 237 Watersplit. AB, RE and SL acknowledge the financial support by the Russian Foundation for Basic Research (Grant No. 17-03-00130-a) and the assistance of the Saint Petersburg State University Computer Center in the accomplishment of high-performance computations.
Ten Facets, One Force Field: The GAL19 Force Field for Water - Noble Metal Interfaces
2020
<div>Understanding the structure of the water/metal interfaces plays an important role in many are as ranging from surface chemistry to environmental processes. Due to their intrinsic complexity, the water/metal interfaces cannot yet be adequately described by quantum mechanical approaches and accurate force-fields are therefore needed. We develop and parametrize GAL19, a novel force-field to describe the interaction of water with two facets (111 and 100) of five metals (Pt, Pd, Au, Ag, Cu). To increase transferability compared to its predecessor GAL17, the water-metal interaction is described as a sum of pair-wise terms. The interaction energy has three contributions: (i) physisorption …
Topology and structure of Au144(SRNH3+)60 from "Atomistic Simulations of Functional Au144(SR)60 Gold Nanoparticles in Aqueous Environment"
2012
Positively charged monolayer-protected gold nanoparticles (AuNPs) structure and topology files for GROMACS used in DOI: 10.1021/jp301094m. The final structure of the simulation reported in DOI: 10.1021/jp301094m for the neutral case is provided. The gold nanoparticle contain a core of 144 Au atoms and 60 functionalized alkanethiol side groups (undecanyl chain, R = C11H22), each possessing a positively charged amonium terminal group. When using this structure do not forget to cite DOI: 10.1021/jp301094m. NOTE1: Different versions for the topology files are provided of both AuNPs. All versions were used for the publication. The changes only affect the core surface and therefore had no influ…
Topology and structure of Au144(SRCOO-)60 from "Atomistic Simulations of Functional Au144(SR)60 Gold Nanoparticles in Aqueous Environment"
2012
Negatively charged monolayer-protected gold nanoparticles (AuNPs) structure and topology files for GROMACS used in DOI: 10.1021/jp301094m. The final structure of the simulation reported in DOI: 10.1021/jp301094m for the neutral case is provided. The gold nanoparticle contain a core of 144 Au atoms and 60 functionalized alkanethiol side groups (undecanyl chain, R = C11H22), each possessing a negatively charged carboxylic terminal group. When using this structure do not forget to cite DOI: 10.1021/jp301094m. NOTE1: Different versions for the topology files are provided of both AuNPs. All versions were used for the publication. The changes only affect the core surface and therefore had no in…
United Atom Force Field for Molecular Dynamics Simulations of 1,4-Polybutadiene Based on Quantum Chemistry Calculations on Model Molecules
1998
We present a united atom force field for simulations of 1,4-polybutadiene based on ab initio quantum chemistry calculations on model molecules. The geometries and energies of conformers and rotational energy barriers in model alkenes and dienes have been determined from high-level quantum chemistry calculations. A rotational isomeric state (RIS) model for 1,4-polybutadiene based on the conformer geometries and energies of the model molecules has been derived. The characteristic ratio and its temperature dependence for cis-1,4-polybutadiene and trans-1,4-polybutadiene, and the characteristic ratio of a random copolymer of cis and trans units, as predicted by the RIS model, are in good agreem…
Millimeter-Scale and Billion-Atom Reactive Force Field Simulation on Sunway Taihulight
2020
Large-scale molecular dynamics (MD) simulations on supercomputers play an increasingly important role in many research areas. With the capability of simulating charge equilibration (QEq), bonds and so on, Reactive force field (ReaxFF) enables the precise simulation of chemical reactions. Compared to the first principle molecular dynamics (FPMD), ReaxFF has far lower requirements on computational resources so that it can achieve higher efficiencies for large-scale simulations. In this article, we present our efforts on scaling ReaxFF on the Sunway TaihuLight Supercomputer (TaihuLight). We have carefully redesigned the force analysis and neighbor list building steps. By applying fine-grained …