A NEW METHOD FOR GENERATING VOLUME CHANGES IN ISOBARIC-ISOTHERMAL MONTE-CARLO SIMULATIONS OF FLEXIBLE MOLECULES

A novel method has been developed to generate volume fluctuations as required in isobaric-isothermal Monte Carlo simulations of flexible (or semi-flexible) chain molecules. While conventional global volume moves entail symmetric changes of the simulation box size, in the new method proposed here, volume changes consist of one-dimensional fluctuations of one of two sections of the system. One of the two sections is a thin slab where all molecular rearrangements are restrained to occur. A deterministic method has been implemented to reposition the molecular segments contained within the slab after a volume change is proposed. The performance of the new method is examined by studying the evolution towards equilibrium of homopolymer hard-core systems upon application of a step increase in the pressure. The new method is shown to be an order of magnitude faster than conventional methods in attaining the equilibrium density of our test systems.