Chempath Shaji, Predescu Cristian, Bell Alexis T
Department of Chemical Engineering, University of California-Berkeley, Berkeley, CA 94720, USA.
J Chem Phys. 2006 Jun 21;124(23):234101. doi: 10.1063/1.2196885.
An algorithm for calculating the partition function of a molecule with the path integral Monte Carlo method is presented. Staged thermodynamic perturbation with respect to a reference harmonic potential is utilized to evaluate the ratio of partition functions. Parallel tempering and a new Monte Carlo estimator for the ratio of partition functions are implemented here to achieve well converged simulations that give an accuracy of 0.04 kcal/mol in the reported free energies. The method is applied to various test systems, including a catalytic system composed of 18 atoms. Absolute free energies calculated by this method lead to corrections as large as 2.6 kcal/mol at 300 K for some of the examples presented.
提出了一种用路径积分蒙特卡罗方法计算分子配分函数的算法。利用相对于参考谐振势的分级热力学微扰来评估配分函数的比值。这里实现了并行回火和一种新的配分函数比值蒙特卡罗估计器，以实现收敛良好的模拟，在所报道的自由能中给出0.04千卡/摩尔的精度。该方法应用于各种测试系统，包括一个由18个原子组成的催化系统。对于所给出的一些例子，用该方法计算的绝对自由能在300K时导致高达2.6千卡/摩尔的校正。
