Study of the structure of molecular complexes. VII. Effect of correlation energy corrections to the Hartree-Fock water-water potential on Monte Carlo simulations of liquid water

Abstract

The two-body Hartree-Fock potential for water-water interactions previously used to describe small water clusters and used in Monte Carlo studies of liquid water has been used to assess the effect of neglecting the correlation energy correction. A number of semiempirical corrections based on the London, Kirkwood, and Wigner formulas were used. They have an energy spread such that they encompass the expected magnitude of the exact correlation energy correction. Short range correlation interactions were included using a modification of the functional of density proposed by Wigner and the corresponding long range interactions were given by a term proportional to r-6 with coefficients due to both London and Kirkwood. After adding the corrections to the Hartree-Fock potential the various potentials were compared by generating a number of potential energy surfaces. Following this the water-water potentials were used in a Monte Carlo simulation of liquid water to calculate thermodynamic and structural data. After comparing the results with experimental data it is seen that the Hartree-Fock potential gives a realistic representation of the structure of liquid water but predicts poor thermodynamic data. Corrrelation energy corrections reduce the discrepancies significantly and it is probable that the remaining error is attributable to many-body effects. The potentials are sufficiently accurate that certain discrepancies in the interpretation of scattering data for liquid water can be indicated. Copyright ©1974 American Institute of Physics.