Condensation/ evaporation coefficient of chain molecules

Abstract

Molecular dynamics (MD) simulations are performed to study the liquid-vapor interface structure of a group of carbon chain molecules: butane (C4H10), octane (C8H18) and dodecane (C12H26) in this paper. The effects of the chain length and temperature on the liquid-vapor interface structure, molecular evaporation/ condensation behavior and the orientation of the liquid-vapor interfacial molecules in equilibrium systems are investigated. It is found that the condensation/ evaporation coefficient of carbon chain molecules primarily depends on the translational energy and the surface temperature similar to simple molecules like argon and water. The MD data of carbon chain molecules agree well with the theoretical expression based on the transition state theory. Also, it is found that the chain ordering at the interface depends on the molecular structure but there's less effect on the condensation/ evaporation behavior at liquidvapor interface. We conclude that the condensation/ evaporation coefficient can be predicted by the translational length ratio of liquid to vapor in general even for the chain molecules. © 2013 The Japan Society of Mechanical Engineers.