Tips for quantum chemical computation (Basic)

Abstract

This article explains the basics of quantum chemical (QC) calculations, which solve the Schrödinger equation numerically by using computers. The QC method is partitioned into two categories: the molecular orbital (MO) method and the density functional theory (DFT). MO, which means a one-electron wave function in a molecule, is commonly expressed by a linear combination of atomic orbitals or basis sets. The Hartree-Fock (HF) method, which is the most fundamental technique in the MO method, constructs many-electron wave functions by an anti-symmetric product of MOs. The MO method can systematically raise the accuracy from the HF method to higher levels of electron correlation theories such as configuration interaction, coupled cluster, and many-body perturbation theories, along with better basis sets. Exchange-correlation functionals, which play a key role in DFT, have a hierarchy: local density approximation (LDA), generalized gradient approximation (GGA), meta-GGA, and hybrid-GGA.