Structural, electronic, and optical properties of orthorhombic and triclinic BiNbO4 determined via DFT calculations
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We performed ab initio calculations using the FPLAW method with the local density approximation (LDA) implemented in the WIEN2 k code for the orthorhombic (α) and triclinic (β) phases of BiNbO4. The modified Becke–Johnson exchange potential (mBJ)-LDA approach was also used to improve the electronic properties. The lattice constants calculated for both structures using the LDA are in good agreement with the experimental values. For the band structure calculations, the mBJ-LDA approach provides reasonable agreement for the band gap value compared with the LDA. The estimated (mBJ)-LDA band gap values are 2.89 eV (3.73 eV) and 2.62 eV (3.15 eV) for the α and β phases of BiNbO4, respectively. Significant optical anisotropy is clearly observed in the visible-light region. We also calculated and evaluated the electron energy loss spectrum for BiNbO4. This work provides the first quantitative theoretical prediction of optical properties and electron energy loss spectra for both the orthorhombic and triclinic phases of BiNbO4.
KeywordsDielectric Function Local Density Approximation BiVO4 Electronic Charge Density Electron Energy Loss Spectrum
R. K. and S. B.O acknowledge support from the National Plan for Science, Technology and Innovation under research project No. 11-NAN1465-02. A. H. R. developed results within the CENTEM project, reg. no. CZ.1.05/2.1.00/03.0088, co-funded by the ERDF as part of the Ministry of Education, Youth and Sports OPRDI program. S.K.G. acknowledges support from the Fulbright-Nehru Postdoctoral Research Fellowship and Department of Science and Technology (DST), Govt. of India. P.K.J. acknowledges the University Grants Commission (UGC) and the Department of Science and Technology (DST), Govt. of India.
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