A HIGH-TEMPERATURE APPROXIMATION FOR THE PATH-INTEGRAL QUANTUM MONTE-CARLO METHOD

A high-temperature approximation for the discretized path-integral qua ntum Monte Carlo (PIQMC) method is formulated. At higher temperatures, all P fictitious classical particles representing a single quantum pa rticle stay close together, and an efficient approximation is obtained when, in the primitive short-time propagator, an essentially local ha rmonic approximation is used for the external potential at the common centre of mass of P fictitious particles-the integration over P - 1 di mensions can then be carried out analytically, and a classical formula of the effective-potential type is obtained for the partition functio n. Also discussed are the proper form and applicability of the virial total-energy estimator for finite systems, and the computation of the temperature dependence of the configurational partition function in a single PIQMC run.