MOLECULAR-DYNAMICS SIMULATION OF LIQUID ALKANES .3. THERMODYNAMIC, STRUCTURAL, AND DYNAMIC PROPERTIES OF BRANCHED-CHAIN ALKANES

Tn recent papers[Bull. Kor. Chem. Sec. 1996, 17, 735; ibid 1997, 18, 4 78] we reported results of molecular dynamics (MD) simulations for the thermodynamic, structural, and dynamic properties of liquid normal al kanes, from n-butane to n-heptadecane, using three different models. T wo of the three classes of models are collapsed atomic models while th e third class is an atomistically detailed model. In the present paper we present results of MD simulations for the corresponding properties of liquid branched-chain alkanes using the same models. The thermodyn amic property reflects that the intermolecular interactions become wea ker as the shape of the molecule tends to approach that of a sphere an d the surface area decreases with branching. Not like observed in the straight-chain alkanes, the structural properties of model III from th e site-site radial distribution function, the distribution functions o f the average end-to-end distance and the root-mean-squared radii of g yration are not much different from those of models I and II. The bran ching effect on the self diffusion of liquid alkanes is well predicted from our MD simulation results but not on the viscosity and thermal c onductivity.