Structural and electronic properties of rare-earth chromites: A computational and experimental study

Abstract

In this work, the structural, optical, and electronic properties of rare-earth perovskites of the general formula $R{\mathrm{CrO}}_{3}$, where $R$ represents the rare-earth Gd, Tb, Dy, Ho, Er, and Tm, have been studied in detail. These compounds were synthesized through a facile citrate route. X-ray diffraction, Raman spectroscopy, and UV-Visible spectroscopy were utilized to reveal the structural evolutions in $R{\mathrm{CrO}}_{3}$. The lattice parameters, ${\mathrm{Cr}}^{3+}--{\mathrm{O}}^{2}--{\mathrm{Cr}}^{3+}$ bond angle, and ${\mathrm{CrO}}_{6}$ octahedral distortions were found to strongly depend on the ionic radii of $R$. First-principles calculations based on density-functional theory within the generalized gradient approximation (GGA) of Perdew-Burke-Ernzerhof (PBE) and strongly constrained and appropriately normed (SCAN) meta-GGA were also employed to calculate the structural and electronic properties of $R{\mathrm{CrO}}_{3}$. The ground-state energy, lattice constants, electronic structures, and density of states of $R{\mathrm{CrO}}_{3}$ were calculated. These provide some insights into the electronic characteristics of the $R{\mathrm{CrO}}_{3}$ compounds. The calculated values of lattice parameters and band gaps with Hubbard $U$ correction ($\mathrm{SCAN}+U$) agree well with values measured experimentally and show more accuracy in predicting the ground-state crystal structure and band structure compared to $\mathrm{PBE}+U$ approximation. The band gap of $R{\mathrm{CrO}}_{3}$ is found to be independent of the ionic radii of $R$ from both experiments and calculations.