Effect of branching on the fluid phase behavior of alkane monolayers
Configurational-bias Monte Carlo simulations in the grand canonical ensemble with histogram reweighting were used to obtain the vapor-liquid coexistence curves of three hexane isomers physisorbed on a flat gold substrate. Examination of the critical ordering operator distributions confirms that these systems exhibit critical behavior consistent with the 2D Ising universality class. The critical temperatures for 2,2-dimethylbutane, 2,3-dimethylbutane, and n-hexane were determined as T(2D)(c) = 195.0, 161.2, and 152.4 K, respectively. This is qualitatively different from the behavior observed for bulk (3D) fluids, where branched alkanes typically exhibit lower critical temperatures than their linear counterparts.
Potoff
JJ
Department of Chemistry and Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA.
Siepmann
JI