Optimized multi-site local orbitals in the large-scale DFT program CONQUEST

TL;DR

This paper presents a numerical optimization method for multi-site support functions in large-scale DFT calculations, improving accuracy and energy minimization in the CONQUEST code.

Contribution

It introduces an optimization approach for multi-site support functions in DFT, enhancing their accuracy and variational properties compared to previous methods.

Findings

Optimization improves accuracy with small cutoffs

Guarantees variational energy minimization

Validated on silicon, benzene, and DNA systems

Abstract

We introduce numerical optimization of multi-site support functions in the linear-scaling DFT code CONQUEST. Multi-site support functions, which are linear combinations of pseudo-atomic orbitals on a target atom and those neighbours within a cutoff, have been recently proposed to reduce the number of support functions to the minimal basis while keeping the accuracy of a large basis [J. Chem. Theory Comput., 2014, 10, 4813]. The coefficients were determined by using the local filter diagonalization (LFD) method [Phys. Rev. B, 2009, 80, 205104]. We analyse the effect of numerical optimization of the coefficients produced by the LFD method. Tests on crystalline silicon, a benzene molecule and hydrated DNA systems show that the optimization improves the accuracy of the multi-site support functions with small cutoffs. It is also confirmed that the optimization guarantees the variational energy minimizations with multi-site support functions.