Spin and orbital magnetic response in metals: susceptibility and NMR shifts

TL;DR

This paper introduces a DFT-based method for calculating all-electron NMR shifts in metals, accounting for both spin and orbital contributions, validated against known data and experiments.

Contribution

It extends the GIPAW method to metals for accurate NMR shift calculations, incorporating both spin and orbital effects.

Findings

Validated against magnetic susceptibility of gases

Accurately computed NMR shifts for simple metals

Method yields ab-initio, experimentally comparable results

Abstract

A DFT-based method is presented which allows the computation of all-electron NMR shifts of metallic compounds with periodic boundary conditions. NMR shifts in metals measure two competing physical phenomena. Electrons interact with the applied magnetic field (i) as magnetic dipoles (or spins), resulting in the Knight shift, (ii) as moving electric charges, resulting in the chemical (or orbital) shift. The latter is treated through an extension to metals of the Gauge Invariant Projector Augment Wave(GIPAW) developed for insulators. The former is modeled as the hyperfine interaction between the electronic spin polarization and the nuclear dipoles. NMR shifts are obtained with respect to the computed shieldings of reference compounds, yielding fully ab-initio quantities which are directly comparable to experiment. The method is validated by comparing the magnetic susceptibility of interacting and non-interacting homogeneous gas with known analytical results, and by comparing the computed NMR shifts of simple metals with experiment.