Numerous different crystal structures of Ta2O5 are reported in literature. Although experimentally and computationally obtained lattice parameters and mechanical properties are in excellent agreement there is a pronounced deviation when it comes to electronic structures of Ta2O5. Based on ab initio studies and nano-beam X-ray diffraction of sputtered Ta2O5 thin films, we introduce an orthorhombic basic structure with a = 0.6425, b = 0.3769, and c = 0.7706 nm, which is stabilized by flipping of an oxygen atom in neighboring c-planes. The calculated energy of formation is with -3.209 eV/atom almost as low as -3.259 eV/atom for the well-known Stephenson superstructure. We propose the new structure based on the fact that it allows for a good description of orthorhombic Ta2O5 even with a small and simple unit cell, which is especially advantageous for computational studies.
@article{arxiv.1404.4347,
title = {Complementary ab initio and X-ray nano-diffraction study of Ta2O5},
author = {R. Hollerweger and D. Holec and J. Paulitsch and M. Bartosik and R. Daniel and R. Rachbauer and P. Polcik and J. Keckes and C. Krywka and P. H. Mayrhofer},
journal= {arXiv preprint arXiv:1404.4347},
year = {2014}
}