Bridge function and other structural properties of core-softened model fluids from molecular dynamics simulations

Molecular dynamics (MD) simulations in three dimensions have been performed for a fluid with particles interacting with a continuous version of the Stell-Hemmer core-softened potential that in two dimensions has been known to reproduce most of the static and dynamic anomalies of liquid water. The pair distribution function obtained from the MD simulation is extrapolated with the help of integral equation theory with a suitable closure relation and the bridge function is extracted. A strong dependence of the bridge function on the system size, i.e., the total number of particles (N) used in the simulation box is observed, which leads to spurious values of the structure factor at long wavelengths. A simple self-consistent correction scheme for the finite size effect has been adopted to correct the bridge function and this scheme produces the correct bridge function even for a small system size. The effects of temperature, number density, and potential parameters on the pair distribution functions and extracted bridge functions are extensively studied.