Computing Electric Field Gradient Tensors

Abstract

The quadrupole coupling observable in solid-state NMR experiments is due to the interaction between the nuclear electric quadrupole moment and the electric field gradient (EFG) tensor. The nuclear moment is a given property of the nucleus studied. The EFG tensor arises from the distribution of charge in the material, so by measuring the coupling we can learn about the bonding in the material. Recent advances in theory and computing power have made the computation of the EFG tensor possible by first-principles methods. In this article we review the ingredients necessary for such computations, their assumptions, and their limitations, and show examples of their use on solid materials. Keywords: electric field gradient (EFG); quadrupole coupling; ab initio methods; density functional theory calculations; projector-augmented wave method