Collective transport in a molecular liquid with quadrupole interaction

Abstract

With three different pair potentials we study the thermal collective transport coefficients of the ${\mathrm{N}}_2$ model liquid by molecular-dynamics calculations. The first two of the considered pair potentials are Lennard-Jones (LJ) one-center and two-center potential functions, while the third represents a two-center LJ function plus a point-quadrupole interaction term. All three potential functions lead to acceptable transport coefficients compared with experiment. However, there appear to be significant differences in the coefficients for certain thermodynamic states. While the quadrupole interaction has only a slight effect on the time correlation functions, the two-center LJ potential influences the time correlation functions appreciably in comparison with the spherically symmetric LJ potential. The latter findings agree well with our previous results obtained for LJ liquids with four or more center potentials. On the whole, the thermal conductivity coefficient is less sensitive to the employed pair potential function than the bulk or the shear viscosity coefficient. Unfortunately there are no experimental data for the bulk viscosity.