Yoshimori Akira
Department of Physics, Kyushu University, Fukuoka, 812-8581, Japan.
J Chem Phys. 2008 Jun 21;128(23):234105. doi: 10.1063/1.2939480.
Validity of the centroid molecular dynamics (CMD) and ring polymer molecular dynamics (RPMD) in quantum liquids is studied on an assumption that momenta of liquid particles relax fast. The projection operator method allows one to derive the generalized Langevin equation including a memory effect for the full-quantum canonical (Kubo-transformed) correlation function. Similar equations for the CMD and RPMD correlation functions can be derived too. The comparison of these equations leads to conditions under which the RPMD and CMD correlation functions agree approximately with the full-quantum canonical correlation function. The condition for the RPMD is that the memory effects of the full-quantum and RPMD equations vanish quickly with the same time constants. The CMD correlation function requires additional conditions concerning static correlation.
在液体粒子动量快速弛豫的假设下，研究了质心分子动力学（CMD）和环聚合物分子动力学（RPMD）在量子液体中的有效性。投影算符方法使人们能够推导出广义朗之万方程，该方程包含了全量子正则（久保变换）关联函数的记忆效应。也可以推导出CMD和RPMD关联函数的类似方程。对这些方程的比较得出了RPMD和CMD关联函数与全量子正则关联函数近似一致的条件。RPMD的条件是全量子方程和RPMD方程的记忆效应以相同的时间常数快速消失。CMD关联函数需要关于静态关联的附加条件。
