Efficient Grid-based Electronic Structure Calculations

Abstract

Density functional theory (DFT) is certainly the most popular method for electronic structure calculations, because it provides a cost-effective means of obtaining reliable results for various applications. Though DFT is formally exact, its numerical accuracy and efficiency is sensitive to the type of basis sets, since it determines the completeness of variational space and the numerical algorithm for solving Schrodinger equation, respectively. Recently, we developed a self-consistent field program based on DFT using Lagrange-sinc functions (LSFs) as a basis set. Though the Lagrange-sinc basis set is based numerical grids, it offers analytical evaluation for Laplacian and some local potential integrals, allowing for rapid and accurate calculations of Hartree terms and pseudopotential integrals. In addition, scalable-parallelization is possible up to thousands cores. Use of multi-grids effectively removes the so-called egg-box effect and greatly reduces computational costs thanks to large grid spacing. We have also extended our code to multiconfiguration methods with a reference configuration obtained from exact exchange Kohn-Sham orbitals, which allows more efficient calculations compared to standard post-Hartree-Fock approaches. In this talk, we present details of our method and numerical results for ground and excited state calculations. [1] Sunghwan Choi, Kwangwoo Hong, Jaewook Kim, and Woo Youn Kim, Accuracy of Lagrange-sinc Functions as a Basis Set for Electronic Structure Calculations of Atoms and Molecules, J. Chem. Phys. 2015, 142, 094116. [2] Jaewook Kim, Kwangwoo Hong, Sunghwan Choi, and Woo Youn Kim, Feature of Exact Exchange Kohn-Sham Orbitals with Krieger-Li-Iafrate Approximation, Bull. Korean Chem. Soc. 2015, 36, 998-1007. [3] Jaewook Kim, Kwangwoo Hong, Sunghwan Choi, Sang-Yeon Hwang, and Woo Youn Kim, Configuration Interaction Singles based on Real-Space Numerical Grid Method: Kohn-Sham versus Hartree-Fock Orbitals, Phys. Chem. Chem. 2015, Phys. in revision.