Molecular dynamics study of the melting of nitromethane

Molecular dynamic studies of melting of nitromethane have been carried out using two methods: (1) void-nucleated melting with the gradual heating of the lattice and (2) equilibration of coexisting liquid and solid phases. The results are in near agreement with each other; the small difference is attributed to the hysteresis effect associated with the direct heating process. The values of the melting temperature T-m computed by using the intermolecular interaction potential of Sorescu [J. Phys. Chem. B 104, 8406 (2000)] are found to be in good agreement with the experimental data at various values of pressure ranging from 1 atm to 30 kbar. The computed values of the melting temperature satisfy the Simon-Glatzel equation P(kbar)=aT(m)(b)+c, where a=1.597x10(-5), b=2.322, c=-6.74, and T-m is in kelvin. A comparison of computed T-m with and without the presence of molecular vibrations reveals that T-m is insensitive to the intramolecular interaction term of the potential energy function, but depends strongly on the intermolecular interactions, particularly the Coulombic term (i.e., the partial charges on atoms). (C) 2003 American Institute of Physics.