PATH-INTEGRAL MONTE-CARLO SIMULATIONS - STUDY OF THE EFFICIENCY OF ENERGY ESTIMATORS

This article presents a study of the relative efficiency of two common ly used energy estimators for path integral Monte Carlo (MC) simulatio ns; the Barker estimator and the virial estimator. Two different path integral MC algorithms are considered; the simple algorithm augmented with whole chain moves and the normal-mode algorithm. The behavior of the two estimators is analyzed in some model systems and the suitabili ty of its application is discussed, considering the general characteri stics of the systems to be simulated. It is concluded that there is no obvious choice when it comes to decide which estimator to use. Instea d, each one may be the most appropriate depending on the specific cond itions of the simulation. Identical conclusions are drawn for both alg orithms considered here. For low temperature systems or with high grad ient potentials, where quantum effects are more significant, the Barke r estimator is to be preferred as the variance of the mean energy is s maller. On the other hand, for high temperature systems or with low gr adient potentials, where quantum effects are less significant, the vir ial estimator has a smaller variance of the mean energy. (C) 1995 Amer ican Institute of Physics.