%0 Journal Article
%T Hidden Structural Order in Orthorhombic Tantalum Pentoxide (Ta$_2$O$_5$)
%A Sung-Hoon Lee
%A Jongseob Kim
%A Sae-Jin Kim
%A Sungjin Kim
%A Gyeong-Su Park
%J Physics
%D 2013
%I arXiv
%R 10.1103/PhysRevLett.110.235502
%X We investigate using first-principles calculations the atomic structure of the orthorhombic phase of Ta$_2$O$_5$. Although this structure has been studied for decades, the correct structural model is controversial owing to the complication of structural disorder. We identify a new low-energy high-symmetry structural model where all Ta and O atoms have correct formal oxidation states of +5 and -2, respectively, and the experimentally reported triangular lattice symmetry of the Ta sublattice appears dynamically at finite temperatures. To understand the complex atomic structure of the Ta$_2$O$_3$ plane, a triangular graph-paper representation is devised and used alongside oxidation state analysis to reveal infinite variations of the low-energy structural model. The structural disorder of Ta$_2$O$_5$ observed in experiments is attributed to the intrinsic structural variations, and oxygen vacancies that drive collective relaxation of the O sublattice.
%U http://arxiv.org/abs/1305.4425v1