蛙跳常用势.ppt

微观尺度材料设计?? 分子动力学 分子动力学的应用-薄膜生长 微观尺度材料设计?? 分子动力学 分子动力学的应用-薄膜生长 微观尺度材料设计?? 分子动力学 微观尺度材料设计?? 分子动力学 微观尺度材料设计?? 分子动力学 分子动力学的应用-高分子链 微观尺度材料设计?? 分子动力学 分子动力学的应用-脆性断裂 微观尺度材料设计?? 分子动力学 分子动力学的应用-晶界行为 微观尺度材料设计?? 分子动力学 分子动力学的应用-纳米晶体 Newton-Raphson Method second derivative method are the most rapidly converging algorithms which require values of function, and its first and second derivatives The memory required for storing the Hessian matrix is proportional to N2 i.e., prohibitive for large macromolecules Minimisation Evolution of substrate temperatures at various incident energy 0.1 eV 10.0 eV Morphologies of Au/Au 001 films at various incident energy 分子动力学的应用-薄膜生长 MD simulation of Cu/Ni multilayer films by IBAD Zhou et al, J. Appl. Phys. 87 2000 No ion bombardment EXe 0.5 eV 分子动力学的应用-薄膜生长 T 300 K T 713 K Epitaxial growth process of SrO on SrTiO3 100 surface terminated by TiO2 atomic layer Kubo et al, J. Chem Phys. 109 1998 * * * * * * * * * * * * May 2001 D. Ceperley Simulation Methods * Parrinello-Rahman simulation 500 KCl ions at 300K First P 0 Then P 44kB System spontaneously changes from rocksalt to CsCl structure Can “automatically” find new crystal structures Nice feature is that the boundaries are flexible But one is not guaranteed to get out of local minimum One can get the wrong answer. Careful free energy calculations are needed to establish stable structure. All such methods have non-physical dynamics since they do not respect locality of interactions. Non-physical effects are O 1/N REFERENCES H. C. Andersen, J. Chem. Phys. 72, 2384 1980 . M. Parrinello and A. Rahman, J. Appl. Phys. 52, 7158 1981 . Constraints in MD Some problems require constraints: fixed bond length water molecule . We would like to get rid of high frequency motion not interesting In LDA-MD we need to keep wavefunctions orthogonal. Putting constraints in “by hand” is difficult for example, working in polar coordinates WARNING: constraints change the ensembl