(223c) Molecular Simulations of the Critical Point for Molecules That Decompose Experimentally

An assumption that has been made by the BYU DIPPR 801 staff in estimating property values for large molecules is that all families eventually converge to the n-alkane family with increasing chain length. For this purpose, much effort has gone into examining the n-alkane family.  Specifically, the properties of n-alkanes as the carbon number approaches infinity have been studied to establish asymptotic convergence to other families. Since the critical point is an essential value for many predictive methods of thermophysical and transport properties, it is particularly important to the DIPPR 801 database.

The difficulty with determining the critical point for large n-alkanes is that their decomposition temperature is much lower than the critical point for carbon chains longer than C10. For this reason, molecular simulations (specifically GEMC in this work) have been a popular means of estimating critical points for thermally unstable molecules. Prior to this work, however, simulations had only been performed to establish a trend for the intermediate sized compounds.

This research focuses on simulating molecules large enough to determine the infinite carbon length behavior. The objective is to determine whether or not the methylene contribution to the critical volume eventually becomes constant. This conclusion will dictate if the critical density approaches a non-zero constant value for an infinite carbon chain.