Mixed valency and site-preference chemistry for cerium and its compounds: A predictive density-functional theory study
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.
- Authors:
-
- Ames Laboratory
- Publication Date:
- Research Org.:
- Ames Lab., Ames, IA (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC)
- OSTI Identifier:
- 1159303
- Report Number(s):
- IS-j 8393
Journal ID: ISSN 1098-0121; PRBMDO; ArticleNumber: 235126
- DOE Contract Number:
- DE-AC02-07CH11358
- Resource Type:
- Journal Article
- Journal Name:
- Physical Review. B, Condensed Matter and Materials Physics
- Additional Journal Information:
- Journal Volume: 89; Journal Issue: 23; Journal ID: ISSN 1098-0121
- Publisher:
- American Physical Society (APS)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 36 MATERIALS SCIENCE
Citation Formats
Alam, Aftab, and Johnson, Duane D. Mixed valency and site-preference chemistry for cerium and its compounds: A predictive density-functional theory study. United States: N. p., 2014.
Web. doi:10.1103/PhysRevB.89.235126.
Alam, Aftab, & Johnson, Duane D. Mixed valency and site-preference chemistry for cerium and its compounds: A predictive density-functional theory study. United States. https://doi.org/10.1103/PhysRevB.89.235126
Alam, Aftab, and Johnson, Duane D. 2014.
"Mixed valency and site-preference chemistry for cerium and its compounds: A predictive density-functional theory study". United States. https://doi.org/10.1103/PhysRevB.89.235126.
@article{osti_1159303,
title = {Mixed valency and site-preference chemistry for cerium and its compounds: A predictive density-functional theory study},
author = {Alam, Aftab and Johnson, Duane D.},
abstractNote = {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.},
doi = {10.1103/PhysRevB.89.235126},
url = {https://www.osti.gov/biblio/1159303},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
issn = {1098-0121},
number = 23,
volume = 89,
place = {United States},
year = {Sun Jun 01 00:00:00 EDT 2014},
month = {Sun Jun 01 00:00:00 EDT 2014}
}