Viscosity of liquid metals: An interpretation

Abstract

The fluidity of liquid metals, like that of simple nonmetallic liquids, is a linear function of the ratio of unoccupied volume to intrinsic volume over long ranges as expressed by the equation varphi = B[(V/V(0)) - 1]. Values of V(0) obtained by extrapolating to varphi = 0 agree well with molal volumes of compact crystals at 20 degrees C calculated from densities.Values of the ratio varphi/[(V/V(0)) - 1] range from 27.0 for Na to 1.55 reciprocal centipoise for Ni. Viscosities at ratios of expansion V/V(0) = 1.10 vary linearly with squares of solubility parameters DeltaE(v)/V(0), where DeltaE(v) is molal energy of vaporization at the melting point. Viscosities at 10% expansion range from 0.037 cP for Na to 5.38 cP for Co, with some divergence for metals with values of eta in the neighborhood of unity. The good agreement in the case of the transition metals Cu, Fe, Co, and Ni we attribute to distribution of vector momentum among quasi-chemical bonds between d-electrons and vacant orbitals.