Efficient Calculations with Multisite Local Orbitals in the large-scale DFT Code CONQUEST

TL;DR

This paper introduces multisite local orbitals in the CONQUEST DFT code, utilizing new methods to enhance efficiency and stability, and demonstrates their accuracy and computational benefits in large-scale systems.

Contribution

It presents a novel implementation of multisite local orbitals with improved methods for stability and efficiency in large-scale DFT calculations.

Findings

Accurate energetic and geometrical properties for Si, Al, and DNA systems

Efficient sparse-matrix multiplications in Hamiltonian construction

Successful representation of occupied and unoccupied band structures

Abstract

Multisite local orbitals, which are formed from linear combinations of pseudo-atomic orbitals from a target atom and its neighbor atoms, have been introduced in the large-scale density functional theory calculation code CONQUEST. Multisite local orbitals correspond to local molecular orbitals so that the number of required local orbitals can be minimal. The multisite support functions are determined by using the localized filter diagonalization (LFD) method [Phys. Rev. B 2009, 80, 205104]. Two new methods, the double cutoff method and the smoothing method, are introduced to the LFD method to improve efficiency and stability. The Hamiltonian and overlap matrices with multisite local orbitals are constructed by efficient sparse-matrix multiplications in CONQUEST. The investigation of the calculated energetic and geometrical properties and band structures of bulk Si, Al and DNA systems demonstrate the accuracy and the computational efficiency of the present method. The representability of both occupied and unoccupied band structures with the present method has been also confirmed.