DFT‐based systematic study on the structural, optoelectronic, thermodynamic, vibrational, and mechanical behavior of Ruddlesden Popper perovskites Sr2XO4 (X = Zr, Hf) for optoelectronic applications

Abstract

AbstractDFT study on the structural, optoelectronic, thermodynamic, vibrational, and mechanical properties of Ruddlesden Popper (RP) perovskites Sr2XO4 (X = Zr, Hf) is made with the help of first principle simulation in the framework of WIEN2K code. The lattice constants in bohr unit are found to be for Sr2ZrO4, and for Sr2HfO4. The calculated band gap values are 2.65 eV for Sr2ZrO4 and 2.58 eV for Sr2HfO4. The band structure and electronic density of states reveal the semiconductor nature of these materials having an indirect band gap. Also, Kramers–Krönig relations are used for optical analysis which unveils that these compounds are suitable for applications in optoelectronic. The vibrational investigations are done while using harmonic approximation. Phonon dispersion curves are plotted to observe the vibrational modes by DFPT to confirm the dynamical stability of studied compounds. Although few soft modes have appeared, however, these compounds are found to be thermally stable. Raman modes appeared at low and high frequencies whereas IR modes are noticed at intermediate frequencies for considered compounds. Upon thermodynamical examination, the maximum value of free energy at 1000 K is noted to be −1.95 eV for Sr2ZrO4 and −2.25 eV for Sr2HfO4. The elastic constants are calculated by using the Voigt–Reuss–Hill approximation. The calculated anisotropic values for these compounds are 1.077 (A) and 0.913 (A) which indicate that Sr2ZrO4 has isotropic behavior and Sr2HfO4 has anisotropic behavior. From our calculations, Voigt Young's modulus of Sr2ZrO4 and Sr2HfO4 is 266.99 (GPa) and 279.42 (GPa) along with Poison's ratio of 0.29 and 0.26, respectively.