Accurate structure factors from pseudopotential methods

TL;DR

This paper demonstrates that an aspherical reconstruction method applied to pseudopotential calculations can accurately reproduce experimental silicon structure factors, matching results from more complex FLAPW methods.

Contribution

It applies a recently developed all-electron charge density reconstruction method to silicon, achieving high accuracy comparable to FLAPW results.

Findings

Aspherical reconstruction matches FLAPW accuracy.

Spherical and frozen core approximations are less accurate.

Reconstructed charge densities reproduce experimental data.

Abstract

Highly accurate experimental structure factors of silicon are available in the literature, and these provide the ideal test for any \emph{ab initio} method for the construction of the all-electron charge density. In a recent paper [J. R. Trail and D. M. Bird, Phys. Rev. B {\bf 60}, 7863 (1999)] a method has been developed for obtaining an accurate all-electron charge density from a first principles pseudopotential calculation by reconstructing the core region of an atom of choice. Here this method is applied to bulk silicon, and structure factors are derived and compared with experimental and Full-potential Linear Augmented Plane Wave results (FLAPW). We also compare with the result of assuming the core region is spherically symmetric, and with the result of constructing a charge density from the pseudo-valence density + frozen core electrons. Neither of these approximations provide accurate charge densities. The aspherical reconstruction is found to be as accurate as FLAPW results, and reproduces the residual error between the FLAPW and experimental results.