Structural, vibrational and electronic properties of LiScO2: A joint experimental and theoretical study

Evolution of structural and vibrational properties of LiScO 2 as observed from the in situ high temperature XRD and Raman spectroscopic studies are presented. Ab initio density functional theory calculations have also been carried out to support them and to derive the electronic properties of LiScO 2 . LiScO 2 exhibits anisotropic expansion with larger expansion along the c- axis (16.5 × 10 −6 K −1 ) compared to a- axis (8.41 × 10 −6 K −1 ). The anisotropy in expansion has been related to the difference in the apical and equatorial Li-O and Sc-O bonds of LiO 6 and ScO 6 octahedra. Overall expansion of unit cell volume is contributed by expansion and distortion of LiO 6 and ScO 6 octahedra. Ab initio phonon calculation revealed 12 Raman active modes but only 8 distinct Raman modes in LiScO 2 . Experimentally, six Raman modes could be identified at ambient and higher temperature, and anharmonic analyses of these modes have carried out. The wavenumbers of all the Raman modes decrease with increasing temperature while a mode at 300 cm −1 is found to be least influenced by temperature. All the modes except that at 300 cm −1 are found to contribute to the expansion of the lattice. Further, equation of states, density of states and band gaps were calculated using density functional theory (DFT). The band gap computed using norm conserving (nc) and LDA or GGA (3.85 or 3.96 eV) agrees well with the band gap (3.96 eV) measured by diffuse reflectance spectroscopy. The calculated bulk modulus (B 0 ) and equilibrium volume (V 0 ) by nc-LDA and nc-GGA are: 119 GPa, 154.8 Å 3 and 104 GPa, 166.3 Å 3 . • Structure, vibrational and electronic properties of LiScO 2 have been reported. • LiScO 2 show high structural stability but strong anisotropic expansions. • Anisotropy in unit cell expansion is related to the distortion and volume of LiO 6 octahedra. • Anharmonic analyses of Raman modes suggest all the modes contribute to the lattice expansion. • LiScO 2 was found to be a direct bandgap semiconductor.