Related Experiment Video
Updated: Jun 19, 2026

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
A stepwise atomic, valence-molecular, and full-molecular optimisation of the Hartree-Fock/Kohn-Sham energy
Branislav Jansík1, Stinne Høst, Mikael P Johansson
1Lundbeck Foundation Centre for Theoretical Chemistry, Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Arhus C, Denmark. jansik@chem.au.dk
Abstract:
A hierarchical optimisation strategy has been introduced for minimising the Hartree-Fock/Kohn-Sham energy, consisting of three levels (3L): an atom-in-a-molecule optimisation, a valence-basis molecular optimisation, and a full-basis molecular optimisation. The density matrix formed at one level is used as a starting density matrix at the next level with no loss of information. To ensure a fast and reliable convergence to a minimum, the augmented Roothaan-Hall (ARH) algorithm is used in both the valence-basis and full-basis molecular optimisations. The performance of the ARH-3L method is compared with standard optimisation algorithms. Both for efficiency and reliability, we recommend to use the ARH-3L algorithm.
More Related Videos
Related Concept Videos
Hybridization of Atomic Orbitals II
Hybridization of Atomic Orbitals I
Atomic Orbitals
Valence Bond Theory and Hybridized Orbitals
A σ bond (single bond in a Lewis structure) is a covalent bond in which the electron density is...
The Energies of Atomic Orbitals
Electronic Structure of Atoms
An atom comprises protons and neutrons, which are contained inside the dense, central core called the nucleus, with electrons present around the nucleus. Taking into account the wave–particle duality of electrons and the uncertainty in position around the nucleus, quantum mechanics provides a more accurate model for the atomic structure. It describes atomic orbitals as the regions around the nucleus where electrons of discrete energy exist, characterized by four quantum numbers: n, l, ml, and...

