Role of atomic radius and d-states hybridization in the stability of the crystal structure of M2O3 (M = Al, Ga, In) oxides

Autor(es)

Sabino, F. P. ; de Oliveira, Luiz Nunes ; Da Silva, Juarez L. F.

• Tipo de documento: Artigo Científico
• Fonte: PHYSICAL REVIEW B; v. 90, n. 15, p. 7-pg., 2014-10-29.

Resumo

We study the stability of the corundum, gallia, and bixbyite structures of Al2O3, Ga2O3, and In2O3 with density functional theory calculations. To artificially control the relative position of the d states within the band structure, we add a Hubbard-like on-site Coulomb interaction to the d states. We quantitatively show that smaller (larger) atomic radii favor the corundum (bixbyte) structure, which supports empirical models based on the atomic radius ratio between the cation and anions and the spacing-filling condition. Thus, Al2O3 and In2O3 crystallizes in the corundum and bixbyite structures, which is consistent with experimental observations. The empirical models based on atomic radius and space filling would predict a corundum or bixbyite structure for Ga2O3. However, as expected from experimental observations, we find gallia to be the most stable structure for Ga2O3. Our results explain why Ga2O3 crystallizes in the gallia structures instead of the corundum or bixbyite as follows. The stability of gallia increases as the hybridization of the Ga d states with the O 2s states grows and the p-d splitting increases, which is maximized by the presence of fourfold cation sites. The presence of the fourfold cation sites in gallia is a key structural feature that increases its relative stability compared with the corundum and bixbyite structures for Ga2O3, which contain only sixfold cation sites, so that the effect of the d states is unimportant. (AU)

• Processo FAPESP: 13/21045-2 - Predição teórica da estrutura, estabilidade termodinâmica, propriedades electronicas e reatividade de nanoclusters
• Beneficiário: Juarez Lopes Ferreira da Silva
• Modalidade de apoio: Auxílio à Pesquisa - Regular