The screening of 4f moments and delocalization in the compressed light rare earths

TL;DR

This study uses dynamical mean field theory to analyze how compression affects 4f electron configurations, moments, and delocalization in light rare earth metals Ce, Pr, and Nd, revealing continuous screening and charge fluctuation changes.

Contribution

It provides a detailed, comparative analysis of 4f electron behavior under compression in Ce, Pr, and Nd, highlighting the role of 4f^{n-1} configurations in delocalization.

Findings

Compression causes screening of 4f moments and increased charge fluctuations.

4f^{n-1} configurations are better indicators of delocalization than 4f^{n+1}.

Similar delocalization trends are observed across Ce, Pr, and Nd.

Abstract

Spin and charge susceptibilities and the 4f^n, 4f^{n-1}, and 4f^{n+1} configuration weights are calculated for compressed Ce (n=1), Pr (n=2), and Nd (n=3) metals using dynamical mean field theory combined with the local-density approximation. At ambient and larger volumes these trivalent rare earths are pinned at sharp 4f^n configurations, their 4f moments assume atomic-limiting values, are unscreened, and the 4f charge fluctuations are small indicating little f state density near the Fermi level. Under compresssion there is dramatic screening of the moments and an associated increase in both the 4f charge fluctuations and static charge susceptibility. These changes are coincident with growing weights of the 4f^{n-1} configurations, which it is argued are better measures of delocalization than the 4f^{n+1} weights which are compromised by an increase in the number of 4f electrons caused by rising 6s, 6p bands. This process is continuous and prolonged as a function of volume, with strikingly similarity among the three rare earths, aside from the effects moderating and shifting to smaller volumes for the heavier members. The observed alpha-gamma collapse in Ce occurs over the large-volume half of this evolution, the Pr analog at smaller volumes, and Nd has no collapse.