Structural, electronic and optical properties of ilmenite and perovskite CdSnO3 from DFT calculations

• Published in: Journal of physics. Condensed matter 2010-11, Vol.22 (43), p.435801-435801
• Main Authors: Sesion Jr, P D, Henriques, J M, Barboza, C A, Albuquerque, E L, Freire, V N, Caetano, E W S
• Format: Article
• Language: English
• Subjects: Absorption; Cadmium Compounds - chemistry; Calcium Compounds - chemistry; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Electric Impedance; Electron density of states and band structure of crystalline solids; Electron states; Electrons; Exact sciences and technology; Iron - chemistry; Lattice dynamics; Models, Molecular; Molecular Conformation; Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; Optical Phenomena; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Other inorganic compounds; Oxides - chemistry; Phonon states and bands, normal modes, and phonon dispersion; Phonons and vibrations in crystal lattices; Physics; Quantum Theory; Spectrophotometry, Infrared; Tin Compounds - chemistry; Titanium - chemistry
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/22/43/435801

CdSnO(3) ilmenite and perovskite crystals were investigated using both the local density and generalized gradient approximations, LDA and GGA, respectively, of the density functional theory (DFT). The electronic band structures, densities of states, dielectric functions, optical absorption and reflectivity spectra related to electronic transitions were obtained, as well as the infrared absorption spectra after computing the vibrational modes of the crystals at q = 0. Dielectric optical permittivities and polarizabilities at ω = 0 and ∞ were also calculated. The results show that GGA-optimized geometries are more accurate than LDA ones, and the Kohn-Sham band structures obtained for the CdSnO(3) polymorphs confirm that ilmenite has an indirect band gap, while perovskite has a direct band gap, both being semiconductors. Effective masses for both crystals are obtained for the first time, being highly isotropic for electrons and anisotropic for holes. The optical properties reveal a very small degree of anisotropy of both crystals with respect to different polarization planes of incident light. The phonon calculation at q = 0 for perovskite CdSnO(3) does not show any imaginary frequencies, in contrast to a previous report suggesting the existence of a more stable crystal of perovskite CdSnO(3) with ferroelectric properties.