Vapor-liquid coexistence properties of complex molecules using temperature expanded grand canonical and isothermal isobaric simulations
MetadataShow full item record
Knowledge of phase coexistence properties help us to understand nature of molecular interactions present in the liquid and vapor phases. A solid understanding of how molecular structure affects VLE and thermophysical properties is a prerequisite for designing new useful molecules and to tune the molecule which can be used for a specific task. Phase equilibria and thermophysical properties is very important for efficient process design and optimization. A Monte Carlo simulation based approach has been applied to evaluate the vapor-liquid co-existence properties of complex molecules over a broad temperature range. General difficulties encountered in performing Monte Carlo simulation of large, flexible compounds have been addressed and sampling of configurational space has been improved using reservoir grand canonical Monte Carlo and expanded ensemble addition and deletion moves. We first discuss the direct determination of coexistence properties via grand canonical and isothermal-isobaric simulations. We then discuss the use of temperature expanded ensemble simulations for tracing coexistence curves over a wide range of temperatures. This strategy reduces computational expenses and avoids the need to overcome large free energy barriers between liquid and vapor phases at low temperatures. The methods were used to find the vapor-liquid coexistence properties of broad range of molecules including non-polar molecules, polar molecules and ionic liquids and results obtained compare very well with simulation data available in the literature.