Temperature rigidity of Rice–Allnatt viscosity across nine liquid sp metals described by the Bretonnet–Silbert pseudopotential

The Bretonnet–Silbert pseudopotential with linearised Weeks–Chandler–Andersen perturbation and Rice–Allnatt transport theory is an sp-band liquid-metal viscosity pipeline used in the literature. We apply it to the nine post-transition sp metals tabulated by Zahid et al. (Zn, Cd, Hg, In, Tl, Sn, Pb, Sb, and Bi) over the Assael IUPAC validity ranges. Two systematic features emerge. For all nine metals, the calculated viscosity ηcalc decreases with temperature a factor of 2.4–6.3 more slowly than experiment ηexp. The ratio ηcalc/ηexp evolves from 0.42–0.83 near the melting temperature to 1.07 ± 0.20 at the upper temperatures, a near-unity crossover reached by seven of the nine metals within their validity ranges. Both depend on the fixed-range soft-tail evaluation (rmax = 10.24 Å) and are not cut-off-converged absolute values. These findings delimit the pipeline’s applicability by quantifying a diagnostic temperature-gradient stiffening and provide a component-resolved benchmark for restoring time-dependent correlations to the friction kernel.