Influence of spin-orbit coupling on chemical bonding

TL;DR

This study investigates how spin-orbit coupling influences chemical bonding and material properties in elemental solids and molecules using high-precision density functional theory, revealing significant volume changes and orbital rearrangements.

Contribution

It provides benchmark-quality all-electron calculations demonstrating the effects of spin-orbit interaction on bonding and volume in heavy elements and elucidates the orbital mechanisms involved.

Findings

Spin-orbit interaction causes volume changes up to 7.6% in heavy elements.

Orbital rearrangements due to spin-orbit coupling affect bonding in diatomic molecules.

Relativistic effects significantly influence chemical bonding in layered materials.

Abstract

The influence of spin-orbit interaction on chemical bonds in elemental solids and homonuclear dimers is analyzed by means of density-functional-theory calculations. Employing highly precise all-electron full-potential methodology, our results represent benchmark quality. Comparison of the scalar- and fully-relativistic approaches for elemental solids shows that the spin-orbit interaction may contract or expand the volume of the considered material. The largest variation of the volume is obtained for Au, Tl, I, Bi, Po and Hg, exhibiting changes between 1.0--7.6\%. Using the tight-binding model, we show for diatomic molecules that the nature of this effect lies in the angular rearrangement of bonding and antibonding orbitals introduced by spin-orbit coupling. Such an angular rearrangement appears in partially filled $p$- or $d$-orbitals in heavy elements. Finally, we discuss the impact of the relativistic effects on the chemical bonding in single-layer iodides and transition metal dichalcogenides