Calculating optical absorption spectra for large systems using linear-scaling density-functional theory

TL;DR

This paper introduces a new linear-scaling density-functional theory method for calculating optical absorption spectra of large systems, using optimized localized orbitals and a projection operator scheme, achieving results comparable to traditional DFT methods.

Contribution

The paper presents a novel LS-DFT approach with a projection operator scheme for accurate unoccupied state representation, implemented in a fully functional code.

Findings

Accurate optical spectra for large molecules achieved

Method shows excellent agreement with traditional DFT results

Efficiently handles large systems with linear scaling

Abstract

A new method for calculating optical absorption spectra within linear-scaling density-functional theory (LS-DFT) is presented, incorporating a scheme for optimizing a set of localized orbitals to accurately represent unoccupied Kohn-Sham states. Three different schemes are compared and the most promising of these, based on the use of a projection operator, has been implemented in a fully-functional LS-DFT code. The method has been applied to the calculation of optical absorption spectra for the metal-free phthalocyanine molecule and the conjugated polymer poly(para-phenylene). Excellent agreement with results from a traditional DFT code is obtained.