First principles study of electronic structure and optical properties of CaTiO3 |
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Authors: | S Saha TP Sinha A Mookerjee |
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Institution: | (1) Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Calcutta 700009, India, IN;(2) SN Bose National Centre for Basic Sciences, JD Block, Sector 3, Salt Lake City, Calcutta 700091, India, IN |
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Abstract: | The electronic-energy band structure, site and angular momentum decomposed density of states (DOS) and charge-density contours
of perovskite CaTiO
3
are calculated by the first principles tight-binding linear muffin-tin orbitals method with atomic sphere approximation using
density functional theory in its local density approximation. The calculated band structure shows an indirect (R-Γ) band gap
of 1.5 eV. The total DOS as well as the partial density of states (PDOS) are compared with the experimental photoemission
spectra. The calculated DOS are in reasonable agreement with the experimental energy spectra and the features in the spectra
are interpreted by a comparison of the spectra with the PDOS. The origin of the various experimentally observed bands have
been explained. From the DOS analysis, as well as charge-density studies, we conclude that the bonding between Ca and TiO
3
is mainly ionic and that the TiO
3
entities bond covalently. Using the projected DOS and band structure we have analyzed the interband contribution to the optical
properties of CaTiO
3
. The real and imaginary parts of the dielectric function and hence the optical constants such as refractive index and extinction
coefficient are calculated. The calculated spectra are compared with the experimental results for CaTiO
3
and are found to be in good agreement with the experimental results. The effective number of electrons per unit cell participating
in the interband transitions are calculated. The role of band structure calculation as regards the optical properties of CaTiO
3
is discussed.
Received 1 February 2000 and Received in final form 21 July 2000 |
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Keywords: | PACS 71 15 Mb Density functional theory local density approximation - 78 20 Ci Optical constants (including refractive index complex dielectric constant absorption reflection and transmission coefficients emissivity) - 77 84 Dy Niobates titanates tantalates PZT ceramics etc |
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