quantum mechanical/molecular mechanical molecular dynamics using multiple-time-scale approach and perturbation theory

多重時間スケール法と摂動法を用いた第一原理量子古典分子動力学法

志賀 基之   ; 立川 仁典*

Shiga, Motoyuki; Tachikawa, Masanori*

第一原理量子古典分子動力学法は法による非経験的な力場計算と経験的な力場計算を組合せたハイブリッド法で、凝集分子系に対して有効なシミュレーション手法として最近注目を集めている。本研究では、第一原理量子古典分子動力学法を用いて熱力学的解析を行うのに適した手法を提案し、その計算効率や計算精度について議論する。また、この手法の有用性を確かめるため、水溶液の構造とエネルギーの計算結果を報告する。

A new computational method is proposed for quantum-mechanical/molecular-mechanical (QM/MM) molecular dynamics (MD) which is limited to time-independent thermodynamic analysis. The idea is to use the mass-scaling method combined with multiple-time-scale algorithm and an approximate QM/MM Hamiltonian derived from the first-order Rayleigh-Schroedinger perturbation theory in which the electronic polarization is neglected as a first approximation. If the polarization effect is not so strong, the correction can also be considered after the simulation run using the weighted sampling method. The advantage and disadvantage of the method is discussed in terms of its computational efficiency and accuracy. As a simple example, we demonstrate an MD simulation of liquid water containing 1 QM molecule and 255 MM molecules, and discuss the advantages in calculating statistical averages such as radial distribution and heat of solution.