Revisiting the Vashishta-Singwi dielectric scheme for the warm dense uniform electron fluid

TL;DR

This paper revisits and corrects the finite temperature Vashishta-Singwi dielectric scheme for warm dense electron fluids, comparing its accuracy with quantum Monte Carlo results and providing guidelines for improved dielectric models.

Contribution

It corrects a thermodynamic derivative error in the Vashishta-Singwi scheme and compares its performance with quantum Monte Carlo data for warm dense electron fluids.

Findings

VS scheme shows structural superiority at strong coupling

STLS scheme has thermodynamic advantages due to error cancellation

Guidelines for constructing more accurate dielectric schemes

Abstract

The finite temperature version of the Vashishta-Singwi (VS) dielectric scheme for the paramagnetic warm dense uniform electron fluid is revisited correcting for an earlier thermodynamic derivative error. The VS scheme handles quantum mechanical effects at the level of the random phase approximation and treats correlations via the density expansion of a generalized Singwi-Tosi-Land-Sj\"olander (STLS) closure that inserts a parameter determined by enforcing the compressibility sum rule. Systematic comparison with quasi-exact results, based on quantum Monte Carlo simulations, reveals a structural superiority of the VS scheme towards strong coupling and a thermodynamic superiority of the STLS scheme courtesy of a favorable cancellation of errors. Guidelines are provided for the construction of dielectric schemes that are expected to be more accurate but computationally costly.