METHODS FOR CONSTRAINING ZERO-POINT ENERGY IN CLASSICAL MONTE-CARLO TRANSITION-STATE THEORY

Two microcanonical sampling methods for constraining zero-point energy (ZPE) within classical Monte Carlo transition-state theory (MCTST) ar e described. Each is based on the efficient microcanonical sampling me thod [H. W. Schranz, S. Nordholm, and G., Nyman, J., Chern. Phys. 94, 1487 !(1991)], with exclusion of phase space paints not satisfying imp osed ZPE constraints, Method 1 requires extensive sampling of phase sp ace points, bur method 2 relies on configurational sampling using a mi crocanonical statistical weight adjusted to account for the reduced lo cal density of momentum states arising from ZPE restrictions. Simple a pplications to HenI2 clusters and a linear model for H-O-D dissociatio n show that there are !significant deviations from standard ?MCTST., M ethods 1 and 2 give similar results, but method 2 is the more efficien t algorithm. (C) 1998 American Institute of Physics. [S0021-9606(98)01 904-7].