TITLE

Properties of amorphous and crystalline titanium dioxide from first principles

AUTHOR(S)
Prasai, Binay; Cai, Bin; Underwood, M.; Lewis, James; Drabold, D.
PUB. DATE
November 2012
SOURCE
Journal of Materials Science;Nov2012, Vol. 47 Issue 21, p7515
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
We used first-principles methods to generate amorphous TiO (a-TiO) models and our simulations lead to chemically ordered amorphous networks. We analyzed the structural, electronic, and optical properties of the resulting structures and compared with crystalline phases. We propose that two peaks found in the Ti-Ti pair correlation correspond to edge-sharing and corner-sharing Ti-Ti pairs. Resulting coordination numbers for Ti (∼6) and O (∼3) and the corresponding angle distributions suggest that local structural features of bulk crystalline TiO are retained in a-TiO. The electronic density of states and the inverse participation ratio reveal that highly localized tail states at the valence band edge are due to the displacement of O atoms from the plane containing three neighboring Ti atoms; whereas, the tail states at the conduction band edge are localized on over-coordinated Ti atoms. The $$\Upgamma$$-point electronic gap of ∼2.2 eV is comparable to calculated results for bulk crystalline TiO despite the presence of topological disorder in the amorphous network. The calculated dielectric functions suggest that the amorphous phase of TiO has isotropic optical properties in contrast to those of tetragonal rutile and anatase phases. The average static dielectric constant and the fundamental absorption edge for a-TiO are comparable to those of the crystalline phases.
ACCESSION #
78437622

 

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