Comment on Reverse Monte Carlo Simulation

Abstract

In a recent paper McGreevy and Pusztai [1] have described an interesting simulation technique for determining the structure of disordered systems (liquids and glasses) that uses as input the experimentally measured radial distribution function g _E(r ₁₂), or equivalently, the structure factor a _E(k). The essence of their procedure is to generate, via Monte Carlo, a set of particle configurations that yield a g(r ₁₂), where r ₁₂ ≡ |r ₂—r ₁| is the distance between particles, that is consistent with g _E(r ₁₂). From these configurations further information about the structure can be extracted, including higher-order correlation functions such as the 3-body function ρ⁽³⁾ (r ₁, r ₂, r ₃) or bond-angle distributions. Although the idea of reverse Monte Carlo (RMC) is not new (see the reference in [1]), McGreevy and co-workers have shown convincingly that it is computationally feasible and have produced results for a variety of liquids, including multicomponent systems. The RMC procedure is certainly appealing; it suggests that the data which is obtained from an X-ray or neutron diffraction experiment can be used to infer more structural information than that which is inherent in the pairwise function g/(r ₁₂). Since, in certain quarters, this is regarded as heresay it is of some interest to ask what is the formal status of the RMC procedure.

Key Words:

• Monte Carlo
• radial distribution function
• pairwise potential
• three body potentials
• liquids
• uniqueness theorem