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Title: Theoretical Characterization of Charge Transport in Chromia (α-Cr2O3)

Abstract

Transport of conduction electrons and holes through the lattice of ?-Cr2O3 (chromia) is modeled as a valence alternation of chromium cations using ab initio electronic structure calculations and electron transfer theory. In the context of the small polaron model, a cluster approach was used to compute quantities controlling the mobility of localized electrons and holes, i.e. the reorganization energy and the electronic coupling matrix element that enter Marcus? theory. The calculation of the electronic coupling followed the Generalized Mulliken-Hush approach and the quasi-diabatic method using the complete active space self-consistent field (CASSCF) method. Our findings indicate that hole mobility is more than three orders of magnitude larger than electron mobility in both (001) and [001] lattice directions. The difference arises mainly from the larger internal reorganization energy calculated for electron transport relative to hole transport processes while electronic couplings have similar magnitudes. The much larger hole mobility vs electron mobility in ?-Cr2O3 is in contrast to similar hole and electron mobility in hematite ?-Fe2O3 previously calculated. Our calculations also indicate that the electronic coupling for all charge transfer processes of interest is smaller than for the corresponding processes in hematite. This variation is attributed to weaker interaction between the metalmore » 3d states and the O(2p) states in chromia than in hematite, leading to smaller overlap between the charge transfer donor and acceptor wavefunctions and smaller super-exchange coupling in chromia. Nevertheless, the weaker coupling in chromia is still sufficiently large to suggest that charge transport processes in chromia are adiabatic in nature. The electronic coupling is found to depend on both the superexchange interaction through the bridging oxygen atoms and the d-shell electron spin coupling within the Cr-Cr donor-acceptor pair, while the reorganization energy is essentially independent of the electron spin coupling.« less

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
15020825
Report Number(s):
PNNL-SA-45498
KC0302010; TRN: US0504728
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 123; Journal Issue: 7
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ATOMS; CATIONS; CHARGE TRANSPORT; CHROMIUM; ELECTRON MOBILITY; ELECTRON TRANSFER; ELECTRONIC STRUCTURE; ELECTRONS; HEMATITE; HOLE MOBILITY; MATRIX ELEMENTS; OXYGEN; POLARONS; SELF-CONSISTENT FIELD; SPIN; TRANSPORT; VALENCE

Citation Formats

Iordanova, Nellie I, Dupuis, Michel, and Rosso, Kevin M. Theoretical Characterization of Charge Transport in Chromia (α-Cr2O3). United States: N. p., 2005. Web. doi:10.1063/1.2007607.
Iordanova, Nellie I, Dupuis, Michel, & Rosso, Kevin M. Theoretical Characterization of Charge Transport in Chromia (α-Cr2O3). United States. https://doi.org/10.1063/1.2007607
Iordanova, Nellie I, Dupuis, Michel, and Rosso, Kevin M. 2005. "Theoretical Characterization of Charge Transport in Chromia (α-Cr2O3)". United States. https://doi.org/10.1063/1.2007607.
@article{osti_15020825,
title = {Theoretical Characterization of Charge Transport in Chromia (α-Cr2O3)},
author = {Iordanova, Nellie I and Dupuis, Michel and Rosso, Kevin M},
abstractNote = {Transport of conduction electrons and holes through the lattice of ?-Cr2O3 (chromia) is modeled as a valence alternation of chromium cations using ab initio electronic structure calculations and electron transfer theory. In the context of the small polaron model, a cluster approach was used to compute quantities controlling the mobility of localized electrons and holes, i.e. the reorganization energy and the electronic coupling matrix element that enter Marcus? theory. The calculation of the electronic coupling followed the Generalized Mulliken-Hush approach and the quasi-diabatic method using the complete active space self-consistent field (CASSCF) method. Our findings indicate that hole mobility is more than three orders of magnitude larger than electron mobility in both (001) and [001] lattice directions. The difference arises mainly from the larger internal reorganization energy calculated for electron transport relative to hole transport processes while electronic couplings have similar magnitudes. The much larger hole mobility vs electron mobility in ?-Cr2O3 is in contrast to similar hole and electron mobility in hematite ?-Fe2O3 previously calculated. Our calculations also indicate that the electronic coupling for all charge transfer processes of interest is smaller than for the corresponding processes in hematite. This variation is attributed to weaker interaction between the metal 3d states and the O(2p) states in chromia than in hematite, leading to smaller overlap between the charge transfer donor and acceptor wavefunctions and smaller super-exchange coupling in chromia. Nevertheless, the weaker coupling in chromia is still sufficiently large to suggest that charge transport processes in chromia are adiabatic in nature. The electronic coupling is found to depend on both the superexchange interaction through the bridging oxygen atoms and the d-shell electron spin coupling within the Cr-Cr donor-acceptor pair, while the reorganization energy is essentially independent of the electron spin coupling.},
doi = {10.1063/1.2007607},
url = {https://www.osti.gov/biblio/15020825}, journal = {Journal of Chemical Physics},
number = 7,
volume = 123,
place = {United States},
year = {2005},
month = {8}
}