Issue 47, 2015

Configuration interaction singles based on the real-space numerical grid method: Kohn–Sham versus Hartree–Fock orbitals

Abstract

We developed a program code of configuration interaction singles (CIS) based on a numerical grid method. We used Kohn–Sham (KS) as well as Hartree–Fock (HF) orbitals as a reference configuration and Lagrange-sinc functions as a basis set. Our calculations show that KS-CIS is more cost-effective and more accurate than HF-CIS. The former is due to the fact that the non-local HF exchange potential greatly reduces the sparsity of the Hamiltonian matrix in grid-based methods. The latter is because the energy gaps between KS occupied and virtual orbitals are already closer to vertical excitation energies and thus KS-CIS needs small corrections, whereas HF results in much larger energy gaps and more diffuse virtual orbitals. KS-CIS using the Lagrange-sinc basis set also shows a better or a similar accuracy to smaller orbital space compared to the standard HF-CIS using Gaussian basis sets. In particular, KS orbitals from an exact exchange potential by the Krieger–Li–Iafrate approximation lead to more accurate excitation energies than those from conventional (semi-) local exchange–correlation potentials.

Graphical abstract: Configuration interaction singles based on the real-space numerical grid method: Kohn–Sham versus Hartree–Fock orbitals

Supplementary files

Article information

Article type
Paper
Submitted
20 Jan 2015
Accepted
31 Mar 2015
First published
01 Apr 2015
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2015,17, 31434-31443

Author version available

Configuration interaction singles based on the real-space numerical grid method: Kohn–Sham versus Hartree–Fock orbitals

J. Kim, K. Hong, S. Choi, S. Hwang and W. Youn Kim, Phys. Chem. Chem. Phys., 2015, 17, 31434 DOI: 10.1039/C5CP00352K

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