Variations in electron density and bonding in the lowest ¹Σ_g state of H₂ molecule under strong magnetic fields by using a time-dependent density functional theory

Abstract

The mechanism of decrease of bond length and the shifting of electronic cusps corresponding to nuclear positions under strong magnetic fields (up to 2.3505 × 10⁹ G) in the lowest ¹Σ_g state (M = 0) of the H₂ molecule is studied by means of a time-dependent density functional equation. The applied magnetic field along the internuclear axis imparts to the electrons an additional motion, resulting in an excess rotational kinetic energy, transverse to the direction of the field. As a result, the electron density contracts towards the internuclear axis, leading to a flow of density from the anti-binding regions behind the nuclei to the binding region between the two nuclei. The consequent shortening of the bond length and the inward shifting of electronic cusps make the molecule more stable even though the overall electronic energy increases as a result of increased kinetic energy. The overall phenomenon may be looked at in terms of a competition between the nuclear electric field and the external magnetic field, which is mainly responsible for the detailed changes in the electron density.