MOLECULAR-DYNAMICS CALCULATION OF THE EQUATION OF STATE OF ALKANES

Molecular dynamics calculations of the pressure in fluids of propane, pentane, and decane show that the pressure in the traditional united-atom model which treats a methylene group as one isotropical interaction unit, scales incorrectly with respect to temperature and density. The shortcoming can, however, easily be overcome by introducing realistic anisotropic intermolecular potential functions. The anisotropy is achieved by taking the geometrical mean position of the valence electrons as the origin for intermolecular interactions of the methylene subunits. © 1990 American Institute of Physics.