Linear scaling DFT calculations for large Tungsten systems using an optimized local basis

TL;DR

This paper demonstrates a linear scaling DFT method using an optimized local basis for large metallic Tungsten systems, enabling efficient simulations of extensive supercells relevant for fusion materials.

Contribution

It introduces a linear scaling DFT approach with an optimized local basis that effectively handles large metallic systems like Tungsten at finite electronic temperatures.

Findings

Linear scaling DFT applied successfully to bulk Tungsten.

The method exploits locality at finite temperature for metals.

Enables large supercell simulations for fusion materials.

Abstract

Density Functional Theory (DFT) has become the quasi-standard for ab-initio simulations for a wide range of applications. While the intrinsic cubic scaling of DFT was for a long time limiting the accessible system size to some hundred atoms, the recent progress with respect to linear scaling DFT methods has allowed to tackle problems that are larger by many orders of magnitudes. However, as these linear scaling methods were developed for insulators, they cannot, in general, be straightforwardly applied to metals, as a finite temperature is needed to ensure locality of the density matrix. In this paper we show that, once finite electronic temperature is employed, the linear scaling version of the BigDFT code is able to exploit this locality to provide a computational treatment that scales linearly with respect to the number of atoms of a metallic system. We provide prototype examples based on bulk Tungsten, which plays a key role in finding safe and long-lasting materials for Fusion Reactors. We believe that such an approach might help in opening the path towards novel approaches for investigating the electronic structure of such materials, in particular when large supercells are required.