SOFTNESS EXPANSION OF GASEOUS TRANSPORT-PROPERTIES .1. DILUTE GASES

Transport properties of dilute gases are studied both analytically and numerically for an inverse power interparticle potential. The mathematical dependence of transport properties on the softness parameter x=n-1 is emphasized, and nonanalytic dependences in x, of the form x2 Inx, are found. The derivation uses Gislason's series expansion for the scattering angle, and confirms and extends a previous result of Baroody. Equilibrium properties are also shown to be nonanalytic in x, but there the nonanalytic contributions are normally insignificant. The results cast doubt on the utility of effective hard-sphere diameter methods for transport theory. In addition, new insight is gained into classical scattering by inverse power potentials.