Document Type

Article

Publication Version

Published Version

Publication Date

6-15-2014

Journal or Book Title

Physical Review B

Volume

89

Issue

23

First Page

235126

DOI

10.1103/PhysRevB.89.235126

Abstract

Cerium and its technologically relevant compounds are examples of anomalous mixed valency, originating from two competing oxidation states—itinerant Ce4+ and localized Ce3+. Under applied stress, anomalous transitions are observed but not well understood. Here we treat mixed valency as an “alloy” problem involving two valences with competing and numerous site-occupancy configurations. We use density-functional theory with Hubbard U (i.e., DFT+U) to evaluate the effective valence and predict properties, including controlling the valence by pseudoternary alloying. For Ce and its compounds, such as (Ce,La)2(Fe,Co)14B permanent magnets, we find a stable mixed-valent α state near the spectroscopic value of νs=3.53. Ce valency in compounds depends on its steric volume and local chemistry. For La doping, Ce valency shifts towards γ-like Ce3+, as expected from steric volume; for Co doping, valency depends on local Ce-site chemistry and steric volume. Our approach captures the key origins of anomalous valency and site-preference chemistry in complex compounds.

Comments

This article is from Phys. Rev. B 89, 235126 (2014), doi:10.1103/PhysRevB.89.235126. Posted with permission.

Copyright Owner

American Physical Society

Language

en

File Format

application/pdf

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