Monte Carlo simulations of liquid and solid nitrogen based on an a b i n i t i o MO–LCAO–SCF–CI potential

Monte Carlo simulations of liquid and solid nitrogen have been performed using intermolecular potentials obtained from quantum mechanical calculations. Essentially, two intermolecular potentials have been used: one calculated with a minimal basis set and the other with an extended basis set including polarization functions. Good agreement with experimental results is obtained provided three conditions are fulfilled: (i) the dispersion interaction must be calculated with a large basis set, (ii) the so called basis set superposition error must be corrected for via counterpoise calculations, and (iii) the quadrupole moment for the monomer must be properly described. Various analytical forms of the intermolecular potential have been tested, and the second virial coefficient has been calculated and shown to be a valuable tool in assessing the accuracy of different intermolecular potentials.