Comparison of polarizable and nonpolarizable models of hydrogen
fluoride in liquid and supercritical states:
A Monte Carlo simulation study
Abstract:
Structural and thermodynamic properties of a polarizable and
two pairwise additive effective interaction potential models
of hydrogen fluoride are analyzed and
compared with experimental data in the liquid and supercritical
phase as well as along the vapor-liquid coexistence line.
Pair correlation functions and thermodynamic
data are obtained from Monte Carlo simulations at two liquid
and four supercritical thermodynamic state points.
Vapor-liquid equilibrium properties have been
calculated from a set of Gibbs ensemble Monte Carlo simulations.
It is found that the polarizable model
is clearly superior over the two nonpolarizable ones in
describing the temperature and density variation of several
thermodynamic and structural properties.
Thus the experimentally observed elongation of the hydrogen
bonds with decreasing density is only reproduced
by the polarizable model. Similarly, among the three models
only the polarizable one can correctly describe the
dependence of the density on the pressure and temperature
in the entire range of the liquid state, although
the density of this model is always somewhat lower than
that of real HF. Consistently, the vapor-liquid coexistence
curve is also much better reproduced by the polarizable
than by the other two models. All three models
underestimate the critical temperature,
although the polarizable model is again in a considerably better
agreement with the experimental data than the other two. All
three models reproduce the experimental fact that the energy
of evaporation of HF goes through
a maximum as a function of the temperature.