Papers by Keyword: Molecular Dynamic Simulation

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Authors: Qi Ming Zhou, Ke Dong Bi, Yun Fei Chen
Abstract: Thermal conductivities of bulk silicon are calculated by equilibrium molecular dynamics (MD) simulations. Applying common used quantum corrections to the MD results, does not bring them into better agreement with the theoretical predictions or experimental data, while the uncorrected values are closer to the theoretical predictions and experiments below 400K. By assessing the validity of quantum corrections according to theoretical calculations and MD simulations, we demonstrate that the hypothesis of equating the heat fluxes is not reliable. In addition, we explore that the rations of thermal conductivities of MD simulations and quantum calculations are approximate to 1. Then a modified quantum correction for mapping MD simulations to quantum systems is proposed.
Authors: A. Suzuki, Yuri M. Mishin
Abstract: We present results of atomistic computer simulations of spontaneous and stress-induced grain boundary (GB) migration in copper. Several symmetrical tilt GBs have been studied using the embedded-atom method and molecular dynamics. The GBs are observed to spontaneously migrate in a random manner. This spontaneous GB motion is always accompanied by relative translations of the grains parallel to the GB plane. Furthermore, external shear stresses applied parallel to the GB and normal to the tilt axis induce GB migration. Strong coupling is observed between the normal GB velocity vn and the grain translation rate v||. The mechanism of GB motion is established to be local lattice rotation within the GB core that does not involve any GB diffusion or sliding. The coupling constant between vn and v|| predicted within a simple geometric model accurately matches the molecular dynamics observations.
Authors: Wen Bin Ni, Jian Wei Zhao, Yun Hong Liu, Feng Ying Wang, Xing Yin
Abstract: Advanced fabrication techniques to miniaturize electromechanical systems have brought us into the regime of nanoelectromechanical systems (NEMS). Understanding the mechanical properties of NEMS components is of fundamental importance in the operation of these devices. In this paper, we have reported the deformation behavior of a single-crystal simply supported nano-beam under the uniformly distributed load. By using the molecular dynamics simulation, we have investigated the influence of span the nano-beam on the bending characters. Due to surface effect, the nano-beam shows a different behavior under the uniformly distributed load.
Authors: Heng An Wu, X.G. Ni, Xiu Xi Wang, K. Haghighi
Authors: Sukky Jun, Young Min Lee, Sung Youb Kim, Se Young Im
Abstract: Molecular dynamics simulation of nanoindentation on Al(111) surface is presented. The simulation is performed using the Ercolessi-Adams glue potential and the Berendsen thermostat. Boundary conditions of 'pseudo' thin film are imposed in order to focus on the dislocation motion in ultra-thin film. Nucleation and development of defects underneath the indenter tip are visualized, and the gliding patterns of dislocation loops are investigated with particular emphasis on the effect of film thickness. Simulation results show that the early emission of dislocation loop is highly dependent on the film thickness.
Authors: Yong Li, Zao Yang Guo, Bei Peng
Abstract: Carbon nanotube has attracted tremendous scientific and industrial interests due to its exceptional mechanical, electrical and thermal properties. In this paper, classic molecular dynamic simulations are carried out to investigate the buckling behaviors and mechanical properties of single-walled carbon nanotubes under axial compression, both for perfect and imperfect ones introducing atomic vacancies. The effect of chirality, diameter, quantity and position of vacancy are systematically studied. The simulation results reveal that their mechanical properties such as Young’s modulus, critical strain and stress suffering a significant decline as the increasing numbers of vacancies. It is also found that the critical stress and strain are sensitive to position of atomic vacancy. Carbon nanotubes with vacancies located at the center have lower critical strain and are easier to reach the failure stage than those with vacancies at both sides.
Authors: Ho Seok Nam, Nong Moon Hwang, B.D. Yu, D.Y. Kim, J.K. Yoon
Authors: Masashi Hirakuri, Toyoki Okumura, Morihiro Saito, Jun Kuwano
Abstract: In order to reproduce the observed ionic conductivities and activation energies computationally, the potential parameters (PMs) were optimized for classical molecular dynamic simulations on Li ion conduction in the A-site deficient perovskite solid solution La056Li0.33TiO3 with disordered A-site ion arrangement. By the use of the optimized PMs, the conductivities and the activation energies were improved considerably from 4.1×10-3 Scm-1 to 4.4×10-2 Scm-1 at 800 K and 0.02 eV to 0.2 eV, respectively. The pair correlation functions calculated with the optimized PMs reveal that the Li-ions are located somewhat broadly mainly in the vicinity of the midpoint between the center of the A-site and the center of the bottleneck formed by four O2-, and that the simulated Li location is significantly related to the conductivity.
Authors: Toyoki Okumura, Ayumi Dodomi, Morihiro Saito, Jun Kuwano
Abstract: The locations and local environments of the Li ions in La0.56Li0.33TiO3 have been investigated by classical molecular dynamics (MD) simulations and first-principles (FP) calculations. The pair correlation functions of Li-O and Li-Ti indicate that the Li ions are located somewhat broadly mainly in the vicinity of the midpoint between the center of the A-site and the center of the bottleneck formed by four O2-. This is consistent well with that suggested from previous neutron diffraction and 6Li-NMR studies. The FP calculations suggest a different location of the Li ion in the vicinity of the midpoint between the centers of two adjcent bottlenecks; however it coincides with one of the locations shown by the trajectories simulated with the MD calculations.
Authors: Hui Qing Lan, Decai Li, Si Wei Zhang
Abstract: The mechanical properties of the molecular deposition film deposited on an Au substrate are studied in the theory for the first time. Firstly, the quantum mechanics have been used to calculate the structure parameters and potential parameters of the molecular deposition film. Secondly, molecular dynamics simulations have been used to study indent process of the molecular deposition film with the action of Au tip. The results showed that an obvious jump to contact appears during the Au tip approaches the molecular deposition film; furthermore, the tilt angle and load of the molecules near the tip have the same tendency of hysteresis, which may be caused by the adhesive force between the tip and the molecular deposition film.
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