Lattice Parameters and Bulk Modulus of SrTi$_{1-\mathit{x}}$Mn$_{\mathit{x}}$O$_{3}$ Perovskites: A Comparison of Exchange-Correlation Functionals with Experimental Validation
We assessed four exchange-correlation functionals (LDA CA-PZ, GGA parametrized by PBE, PBEsol, and WC) in predicting the lattice parameters of SrTi$_{1-\mathit{x}}$Mn$_{\mathit{x}}$O$_{3}$ perovskites, assuming cubic structures. Predictions were verified using X-ray diffraction (XRD) for Mn content of $\mathit{x}$ = 0.0, 0.1, 0.2, 0.3, 0.5, 1.0, confirming cubic symmetry and a linear decrease in lattice parameters with increasing Mn. PBEsol and WC demonstrated the highest precision (deviations < 0.20%). Additionally, bulk moduli were calculated using the same functionals and verified with the experimental bulk modulus of SrTiO$_{3}$ (183 $\pm$ 2 GPa, Pulse-Echo method). The predicted bulk moduli exhibited a slow, linear increase with increasing Mn. The best correspondence with the experimental bulk modulus was achieved by PBEsol and WC (deviations < 0.7%). These findings highlight the reliability of PBEsol and WC functionals for accurately modeling structural properties of SrTi$_{1-\mathit{x}}$Mn$_{\mathit{x}}$O$_{3}$ perovskites, having better precision than commonly employed LDA and PBE functionals.