Accurate and efficient structure factors in ultrasoft pseudopotential and projector augmented wave DFT

TL;DR

This paper introduces a new method to efficiently compute accurate structure factors in plane-wave DFT using ultrasoft pseudopotentials and PAW, reducing computational cost while maintaining high accuracy.

Contribution

The authors develop a grid-separation approach leveraging projector functions to compute structure factors without dense real-space grids, improving efficiency in plane-wave DFT calculations.

Findings

Achieves all-electron accuracy in structure factors

Validates method against experimental and all-electron DFT data

Reduces computational cost compared to previous methods

Abstract

Structure factors obtained from diffraction experiments are one of the most important quantities for characterizing the electronic and structural properties of materials. Methods for calculating this quantity from plane-wave density functional theory (DFT) codes are typically prohibitively expensive to perform, requiring the electron density to be constructed and evaluated on dense real-space grids. Making use of the projector functions found in both the Vanderbilt ultrasoft pseudopotential and projector augmented wave methods, we implement an approach to calculate structure factors which avoids the use of a dense grid by separating the rapidly changing contributions to the electron density and treating them on logarithmic radial grids. This approach is successfully validated against structure factors obtained from all-electron DFT and experiments for three prototype systems, allowing structure factors to be obtained at all-electron accuracy at a fraction of the cost of previous approaches for plane-wave DFT.