A GRAND-CANONICAL ENSEMBLE MONTE-CARLO STUDY OF THE EFFECTS OF CHANGEOF CORE SIZE ON THE THERMODYNAMIC PROPERTIES OF A MODIFIED LENNARD-JONES FLUID

It is shown by consideration of the fundamental theory that when deali ng with potentials having hard cores the Grand Canonical Ensemble Mont e Carlo (GCEMC) method should not introduce large errors of the type p reviously found in the use of the Shing-Gubbins (SG) method for estima tion of the chemical potential. This is confirmed by making simulation runs using the GCEMC and the Canonical Ensemble Monte Carlo (CEMC) me thods on similar systems having the hard-core Lennard-Jones intermolec ular potential. Only when the hardcore parameter (alpha) (where the ha rd-core diameter is alpha sigma, sigma being the Lennard-Jones length parameter) is increased from 0.9 to 0.95 are appreciable changes in de nsity and reduced potential energy (for a given mu) found. Correspondi ng, though much larger, changes in the fluctuations quantities f(NN)(= [N-2] - [N](2)) and f(NU)(= [NUN] -[N][U-N]), though not inf(NU)/f(NN ), also occur.