Approximate Formula for Bulk Viscosity

We derive a new approximate formula for the bulk viscosity in terms of microscopic information such as the interatomic potential phi(r) and the pair distribution function g(r). This is a unique characteristic of this expression when compared with the previously proposed formulae in which the bulk viscosity zeta is expressed in terms of pressure. Debye relaxation is assumed for g(r) in the derivation of this approximate formula, and it is an effective method of determining a correct order of magnitude. This is confirmed by performing simulations of a Leonard-Jones fluid near its triple point.