First-Principles Study of Electronic, Elastic, and Lattice Vibrational Properties of Pbnm Orthorhombic SrHfO₃

Abstract

Through first-principles pseudopotential calculations based on density functional theory, the electronic structure and lattice vibrational properties of Pbnm orthorhombic SrHfO₃ were investigated in the framework of standard functional approximation and density functional perturbation theory, respectively. The calculated equilibrium lattice constants of Pbnm orthorhombic SrHfO₃ are in good agreement with available experimental and theoretical results. The results show that Pbnm orthorhombic SrHfO₃ is an insulator with a direct band gap of 3.9 eV and 4.0 eV within the calculations using local density approximation (LDA) and generalized gradient approximation (GGA), respectively. Use of the screened exchange local density approximation (sX-LDA) as a functional in a successive band calculation has also been performed. The band gap is predicted to be 6.7 eV within sX-LDA, somewhat higher than the gap values of 6.1 ± 0.1 eV and 6.5 eV obtained from recent x-ray photoelectron spectroscopy. The phonon dispersion curves of Pbnm orthorhombic SrHfO₃ were also calculated. All-positive phonon frequencies were observed in the whole Brillouin zone, indicating stability of the Pbnm orthorhombic SrHfO₃ structure. In addition, the infrared-active and Raman-active vibrational modes of SrHfO₃ were calculated and compared with available theoretical and experimental investigations.