Ab initio insight into the physical properties of new ferroelectric perovskite oxide materials XGeO3 (X = Sr, Ca)

Abstract

The investigation of structural stability, electronic, mechanical, spontanous polarization, and thermodynamic properties of simple cubic perovskite oxides XGeO3 (X =Sr, Ca) has been performed through density functional theory as introduced in Wien2K code. The tolerence factor, Born criteria, and phonon dispersion confirm the stability and the formation of both materials in the ideal cubic structure. Additionally, the application of nmBJ approach in electronic properties shows an exceptional semiconducting aspect. The strain effect on spontaneous polarization of XGeO3 (X =Sr, Ca) perovskites presents an excellent ferroelectric behavior. The thermodynamic parameters such as volume, bulk modulus, thermal expansion coefficient, Debye temperature, Gibbs free energy, enthalpy, heat capacities, and Gruneisen, have been ¨ calculated and discussed with a wide range of pressures (0−20 GPa) and temperatures (0−1000 K). Based on the exceptional semiconducting nature and significant spontaneous polarization, the studied materials can be considered as ferroelectric materials, which make them as a suitable candidates in ferroelctric devices.