New method for equation-of-state calculations: Linear combinations of basis potentials

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Abstract
A new method presented here for calculating the equation of state for classical systems is very fast, employs the same algorithm for all solid and fluid densities and temperatures, and is of accuracy comparable with that of the computer simulations. The method consists of fitting the pair potential by a linear combination of potentials belonging to a basis set (for which the inverse power potentials are a good choice) and of employing a property of additivity of equations of state when these are considered in terms of the density and excess entropy as the independent variables. The new method accomodates the static lattice sum, or any physical quantity that is expected to be additive in pair-potential contributions, as naturally as the pair potential itself, and should be very useful in the study of equations of state for real materials. There are indications for the validity of the new method in two dimensions as well.