Computational extensive investigation of the structural, electronic, magnetic, mechanical, and optical properties of calcium-doped LaMnO3 via DFT+U

Abstract

Perovskite oxides, particularly lanthanum manganite (LaMnO₃), have garnered significant attention due to their exceptional electronic, magnetic, and optical properties, which make them highly promising for applications in spintronics, optoelectronics, and energy storage. In this study, we use density functional theory (DFT) with the generalized gradient approximation plus Hubbard U correction (GGA + U) to systematically investigate the structural, electronic, magnetic, optical, and mechanical properties of pristine LaMnO₃ and its calcium-doped variant (Ca-doped LaMnO₃). The Wien2k software package was employed for the calculations, incorporating a 4 eV Hubbard U parameter to account for the Mn-3d orbital electron-electron correlation strength. The simulation results show that pristine LaMnO₃ exhibits a well-defined bandgap in the spin-up channel, which confirms its insulating nature. However, the spin-down channel displays either a diminished or absent bandgap due to intense exchange interactions and Jahn-Teller distortions. The introduction of Ca dopants creates holes that reduce the bandgap, transforming the material from an insulating to a metallic state. The magnetic moments in pristine LaMnO₃ localize exclusively on manganese ions, generating a total spin magnetic moment of 7.99904, which confirms its strong antiferromagnetic ordering. After Ca doping, the total spin magnetic moment decreases to 3.00126, indicating a reduced magnetic strength and an increase in metallic properties. The introduction of Ca in LaMnO₃ results in significant modifications to the optical properties, including the dielectric function, absorption, reflectivity, and energy loss rates. The dielectric function analysis reveals that doping leads to a reduction of the bandgap and a shift toward metallic behavior, particularly in the spin-down channel. Further analysis of absorption and refractive index spectra demonstrates that Ca doping enhances material conductivity while diminishing its insulating properties. Additionally, the bulk modulus, shear modulus, and Young modulus decrease after Ca doping, making the material more prone to deformation.