Issues and Challenges in Orbital-free Density Functional Calculations

TL;DR

This paper discusses the computational challenges in orbital-free density functional calculations, focusing on functional quality, pseudo-potential construction, and solution algorithm stability, supported by performance testing on various systems.

Contribution

It introduces and evaluates modified-conjoint GGA kinetic energy functionals, addressing stability, speed, and accuracy issues in orbital-free DFT calculations.

Findings

Modified-conjoint GGA functionals improve accuracy

Performance varies between all-electron and pseudo-potential methods

Computational stability depends on functional choice and algorithms

Abstract

Solving the Euler equation which corresponds to the energy minimum of a density functional expressed in orbital-free form involves related but distinct computational challenges. One is the choice between all-electron and pseudo-potential calculations and, if the latter, construction of the pseudo-potential. Another is the stability, speed, and accuracy of solution algorithms. Underlying both is the fundamental issue of satisfactory quality of the approximate functionals (kinetic energy and exchange-correlation). We address both computational issues and illustrate them by some comparative performance testing of our recently developed modified-conjoint generalized gradient approximation kinetic energy functionals. Comparisons are given for atoms, diatomic molecules, and some simple solids.