Molecular Dynamics Study on Evaporation Coefficient of Long-Chain Molecules

Abstract

A simple theoretical expression for the evaporation/condensation coefficient in equilibrium has been proposed by Nagayama and Tsuruta based on the transition state theory and molecular dynamics simulations in 2003. It is not clear, however, whether this approach can be applied to complex molecules such as n-dodecane with long chain structures.In this study, molecular dynamics (MD) simulations have been performed to investigate the evaporation/condensation coefficients of n-dodecane in equilibrium systems. It is found that the evaporation coefficient of n-dodecane primarily depends on the translational energy and the surface temperature similar to simple molecules like argon and water, while the molecular orientation of long chain n-dodecane has less effect. Also, the MD data of n-dodecane agree well with the theoretical expression based on the transition state theory. We conclude that the evaporation coefficient can be predicted by the translational length ratio of liquid to vapor in general even for the long-chain molecules.

Molecular dynamics study of the processes in the vicinity of the n-dodecane vapour/liquid interface

“…As follows from this figure, there is a general agreement between the present results, the predictions of the transition state theory, and the prediction of [37], although the reasons for noticeable deviation between these results are still to be investigated. One of the reasons could be linked with the limited number of molecules used in our calculations.…”

“…The molecular dynamics simulation of n-dodecane (C 12 H 26 ) in an equilibrium system has been also performed using AMBER version 10.0 (a package of molecular simulation programmes) [37]. In that paper, the general Amber force field (GAFF) has been applied and the potential energy has been presented as a sum of bending, torsion, van der Waals and Coulomb energies.…”

Modelling of Evaporation of Clusters and Nanodroplets of Organic Molecules Using Quantum Chemical and the Kinetic Gas Theory Methods

“…Its value was calculated with the molecular dynamics (MD) in which the interaction between individual molecules was described by the force field (FF) methods simplifying both interand inner-molecular interactions by ignoring electrons per se (i.e. quantum effects were ignored) [14,15,[18][19][20]. Alternative quantum mechanical approaches used to analyse the droplet evaporation process were recently developed [21][22][23][24][25].…”

“…Therefore, the clustered structure of alkanes is less probable than that of water, however, is possible. These alkanes features allow a certain simplicity of the modelling, including the application of molecular mechanics (MM) and molecular dynamics methods based on the vdW force field approaches [16,[18][19][20]. These models can be applied to both individual liquids and complex mixtures including a number of compounds which can be evaporated under various conditions [29][30][31][32][33][34][35][36].…”