A molecular dynamics study of the influence of elongation and quadrupole moment upon some thermodynamic and transport properties of linear heteronuclear triatomic fluids

The influence of elongation, quadrupole strength, temperature, and number density upon the pressure, energy, translational diffusion, rotational relaxation, and shear viscosity of linear, rigid, three-site, heteronuclear, shifted-force Lennard-Jonesiums (RTSLJ) was studied via (N,V,T) molecular dynamics. For quadrupolar systems, molecular elongation was systematically perturbed about a base case, with quadrupole strengths scaling as the square of the elongation. The same elongation perturbations were applied to otherwise identical, nonquadrupolar systems. At constant density, the configurational energy increases in magnitude with elongation for the quadrupolar systems, and decreases in the nonquadrupolar case. The pressure exhibits a maximum at intermediate elongation in the presence of quadrupolar interactions, and increases monotonically with elongation at constant density for nonquadrupolar systems. Center-of-mass mobility decreases due to the presence of quadrupolar interactions, which also tend to slow down rotational relaxation rates.