X-ray diffraction experiments, luminescence measurements and first-principles GGA+U calculations on YTaO4

• Published in: Computational materials science 2013-09, Vol.77, p.13-18
• Main Authors: Lim, Thong Leng, Nazarov, Mihail, Yoon, Tiem Leong, Low, Lay Chen, Ahmad Fauzi, M.N.
• Format: Article
• Language: English
• Subjects: Ab initio calculations; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conduction band; Density of states; DOS; Electron density of states and band structure of crystalline solids; Electron states; Electronic structure; Energy gap; Exact sciences and technology; Exchange; Hubbard energy; Luminescence; Mathematical analysis; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other inorganic compounds; Other solid inorganic materials; Photoluminescence; Physics; Tantalum; YTaO4; Yttrium
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2013.03.042

•GGA+U calculation shows that a band gap of 5.1eV of the host lattice can be accommodated.•The composition and structure of the valence and conduction bands of the tantalate system are calculated.•The calculated DOS compared well with the excitation spectra. The structural and electronic properties of yttrium tantalate (YTaO4) crystal are studied using experimental and first-principles total energy calculations. The band gap of the host lattice from absorption and luminescence experiment is measured to be 5.1eV. This is close to 5.14eV reproduced by means of GGA+U approach. In our calculation, we tune both the Hubbard energy U and the exchange parameter J to reproduce the energy gap measured experimentally. It is found that the Hubbard energy U plays a major role in reproducing the experimentally measured energy gap but the exchange parameter J does not. We also calculate the density of states (DOS) using the optimized U to interpret the experimentally measured luminescence spectra. Both the experimental and DOS calculation show that the valence band of tantalate (Ta) system is mainly composed of oxygen (O) 2p states. The lower conduction band is mainly composed of Ta 5d states, while the upper conduction band involves contribution mainly from yttrium (Y) 4d states, with the middle conduction band mainly a mixture of Ta and Y states.