Within the Li<sub>x</sub>La<sub>2/3-x/3</sub>□ <sub>1/3-2x/3</sub>TiO<sub>3</sub> (LLTO) solid electrolytes with perovskite superstructures, the x = 0.125 term was selected as representative of the Li-poor compositions. Two ordered structural models, with Z=8 formula units per 2a<sub>p</sub> × 2a<sub>p</sub> × 2a<sub>p</sub> unit-cell, were considered for ab initio periodic quantum-mechanical calculations (DFT-B3LYP Hamiltonian, Gaussian-atomic-orbital basis set). Least-energy optimizations showed that model 1, with P2mm symmetry, is more stable and agrees with the Cmmm disordered structures of the x = 0.16 and 0.18 terms from experiment. Then the energy of nonequilibrium states with displaced Li positions ("frozen ion" approach) and lowered symmetry was computed, determining mobility paths of the Li<sup>+</sup> ion within the (001) layers of both models. A one-dimensional [100] pathway with activation barrier of 0.42 eV was found in the 2La+1Li+1□ layer of model 2, and a two-dimensional one (0.47 eV barrier) in the 1La+1Li+2□ layer of model 1. Both Li<sup>+</sup> ion transport mechanisms should operate in the real disordered material. The predicted barriers are discussed and compared with the experimental activation energy of Li-richer terms. © 2008 American Chemical Society.

Catti, M. (2008). Ion Mobility Pathways of the Li+ Conductor Li0.125La0.625TiO3 by Ab Initio Simulations. JOURNAL OF PHYSICAL CHEMISTRY. C, 112(29), 11068-11074 [10.1021/jp803345y].

Ion Mobility Pathways of the Li+ Conductor Li0.125La0.625TiO3 by Ab Initio Simulations

CATTI, MICHELE
2008

Abstract

Within the LixLa2/3-x/31/3-2x/3TiO3 (LLTO) solid electrolytes with perovskite superstructures, the x = 0.125 term was selected as representative of the Li-poor compositions. Two ordered structural models, with Z=8 formula units per 2ap × 2ap × 2ap unit-cell, were considered for ab initio periodic quantum-mechanical calculations (DFT-B3LYP Hamiltonian, Gaussian-atomic-orbital basis set). Least-energy optimizations showed that model 1, with P2mm symmetry, is more stable and agrees with the Cmmm disordered structures of the x = 0.16 and 0.18 terms from experiment. Then the energy of nonequilibrium states with displaced Li positions ("frozen ion" approach) and lowered symmetry was computed, determining mobility paths of the Li+ ion within the (001) layers of both models. A one-dimensional [100] pathway with activation barrier of 0.42 eV was found in the 2La+1Li+1□ layer of model 2, and a two-dimensional one (0.47 eV barrier) in the 1La+1Li+2□ layer of model 1. Both Li+ ion transport mechanisms should operate in the real disordered material. The predicted barriers are discussed and compared with the experimental activation energy of Li-richer terms. © 2008 American Chemical Society.
Articolo in rivista - Articolo scientifico
lithium ion conductivity; ab initio simulations
English
2008
112
29
11068
11074
none
Catti, M. (2008). Ion Mobility Pathways of the Li+ Conductor Li0.125La0.625TiO3 by Ab Initio Simulations. JOURNAL OF PHYSICAL CHEMISTRY. C, 112(29), 11068-11074 [10.1021/jp803345y].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/13307
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