David S. Corti (Purdue University Chemical Engineering)


Location: Radiation Laboratory Auditorium

Molecular Simulations in the Isothermal-Isobaric Ensemble: The Requirement of a "Shell" Particle

Since most experimental observations are performed at constant temperature and pressure, the isothermal-isobaric (NPT) ensemble has been widely used in molecular simulations.  Nevertheless, the statistical mechanical formalism of the NPT ensemble has only recently been placed on a rigorous foundation (e.g., Koper and Reiss, 1996, J. Phys. Chem. 100, 422; Corti, 2001, Phys. Rev. E 64, 016128). In particular, the proper statistical mechanical formulation of the NPT ensemble requires a “shell” particle to uniquely identify the volume of the system, thereby avoiding the redundant counting of configurations. Current constant pressure simulation algorithms are, however, not consistent with this recent reformulation. To date, only modifications of the NPT Monte Carlo (MC) method have been derived (Corti, 2002, Mol. Phys. 100, 1887), in which the shell particle is used to define the system volume.