65 resultados para Langevin dynamics
Resumo:
Adhesion forces of Dipalmitoylphosphatidylcholine ( DPPC) membrane in the gel phase are investigated by molecular dynamics ( MD) simulation. In the simulations, individual DPPC molecules are pulled out of DPPC membranes with different rates and we get the maximum adhesion forces of DPPC membrane. We find that the maximum adhesion forces increase with pull rate, from about 400 to 700 pN when pull rates are from 0.001 to 0.03 nm/ps. We analyze the relationship between pull rate and adhesion forces of different origins using Brownian dynamics and notice that viscosity of solvent plays an important role in adhesion forces. Then we simulate the motion of a single DPPC molecule in solvent and it elucidates that the maximum drag force is almost linear with respect to the pull rate. We use Stokes' relation to describe the motion of a single DPPC molecule and deduce the effective length of a DPPC molecule. Conformational analyses indicate that the free energy variation of a DPPC molecule inside and outside of the DPPC membrane is an essential part of adhesion energy.
Resumo:
This book elucidates the methods of molecular gas dynamics or rarefied gas dynamics which treat the problems of gas flows when the discrete molecular effects of the gas prevail under the circumstances of low density, the emphases being stressed on the basis of the methods, the direct simulation Monte Carlo method applied to the simulation of non-equilibrium effects and the frontier subjects related to low speed microscale rarefied gas flows. It provides a solid basis for the study of molecular gas dynamics for senior students and graduates in the aerospace and mechanical engineering departments of universities and colleges. It gives a general acquaintance of modern developments of rarefied gas dynamics in various regimes and leads to the frontier topics of non-equilibrium rarefied gas dynamics and low speed microscale gas dynamics. It will be also of benefit to the scientific and technical researchers engaged in aerospace high altitude aerodynamic force and heating design and in the research on gas flow in MEMS
| [1] Molecular structure and energy states | (21) | ||
| [2] Some basic concepts of kinetic theory | (51) | ||
| [3] Interaction of molecules with solid surface | (131) | ||
| [4] Free molecular flow | (159) | ||
| [5] Continuum models | (191) | ||
| [6] Transitional regime | (231) | ||
| [7] Direct simulation Monte-Carlo (DSMC) method | (275) | ||
| [8] Microscale slow gas flows, information preservation method | (317) | ||
| [App. I] Gas properties | (367) | ||
| [App. II] Some integrals | (369) | ||
| [App. III] Sampling from a prescribed distribution | (375) | ||
| [App. IV] Program of the couette flow | (383) | ||
| Subject Index | (399) | ||
Resumo:
The influence of water on the brittle behavior of beta-cristobalite is studied by means of molecular dynamics (MD) simulation With the TTAM potential. Crack extension of mode 1 type is observed as the crack opening is filled LIP With water. The critical stress intensity factor K-lc(MD) is used to characterize the crack extension of MD simulation. The surface energy of SiO2 covered with layers of water is calculated at temperature of 300 K. Based oil the Griffith fracture criterion, the critical stress intensity factor K-lc(Griffith) is calculated, and it is in good agreement with that of MD simulation. (C) 2008 Elsevier B.V. All rights reserved.
Resumo:
The tension and compression of single-crystalline silicon nanowires (SiNWs) with different cross-sectional shapes are studied systematically using molecular dynamics simulation. The shape effects on the yield stresses are characterized. For the same surface to volume ratio, the circular cross-sectional SiNWs are stronger than the square cross-sectional ones under tensile loading, but reverse happens in compressive loading. With the atoms colored by least-squares atomic local shear strain, the deformation processes reveal that the failure modes of incipient yielding are dependent on the loading directions. The SiNWs under tensile loading slip in {111} surfaces, while the compressive loading leads the SiNWs to slip in the {110} surfaces. The present results are expected to contribute to the design of the silicon devices in nanosystems.
