Monte Carlo simulation of isopentane glass

Abstract

Monte Carlo calculations on liquid and glassy isopentane have been performed by using transferable intermolecular potential functions (t.i.ps). Thermodynamic properties, radial distribution functions, coordination number distributions, etc., calculated for the liquid are in reasonable agreement with the experimental values. By quenching the liquid, we have obtained the glass-transition temperature from the temperature variation of intermolecular energy, volume and the heat of vaporization. Radial distribution functions suggest a structure of the glass primarily influenced by geometrical factors and with no preference for any particular orientation; the peak around 4.0 Å=(1Å=10⁻¹⁰m=10⁻¹ nm) between the more exposed carbon atoms seems to be the characteristic of densely packed hydrocarbons. The histogram of the nearest-neighbour distribution shows a shift towards higher coordination in the glassy state. Interesting differences are found between the liquid and the glass in the dimerization energy and bonding energy distribution functions. Narrower distribution is found on vitrification in the dihedral angle distribution function for rotation around the central C-C bond.