Structural, magnetic, electronic, optical and mechanical properties of actinide perovskite oxides XAnO3 [X = Cs+, Ba2+; An = Np5+, Np4+]: GGA, GGA+U and GGA+U+mBJ investigations

Abstract

First-principles density functional theory (DFT)-based calculations were performed to investigate the structural, magnetic, electronic, optical and mechanical properties of two actinide perovskite oxides XAnO₃, where [X = Cs⁺, Ba²⁺; An = Np⁵⁺, Np⁴⁺]. Wien2k software is utilized with GGA, GGA + U and GGA + U + mBJ potentials. The unit cell volumes for cubic (Pm-3m) structure of XAnO₃ are optimized to achieve the ground state energy and equilibrium parameters. Substitution of X- and An-sites increases the lattice constant, $a_0$ = 4.3998 Å (X = Cs⁺) and $a_0$ = 4.4378 Å (X = Ba²⁺). The calculated band structure plus total and partial density of states using these methods confirm the 100 % spin-polarization and half-metallic (HM) nature of XAnO₃ with $E_g^{\downarrow }$ = 2.731, 3.896 and 3.787 eV (X = Cs⁺); 3.891, 3.929 and 4.329 eV (X = Cs⁺). Total magnetic moment per unit cell of XAnO₃ is respectively $M^{Tot}$ = 2.0 and 3.0 μ_B revealing their ferromagnetic (FM) behavior with high Curie temperature ($T_C$) within GGA, GGA + U and GGA + U + mBJ. Mechanical and thermodynamic stability of XAnO₃ have been proved via the elastic parameters, sound velocity, Debye and melting temperatures, and enthalpy of formation. In addition, XAnO₃ show amazing optical responses include high absorption, conductivity, refractivity, and reflectivity. These investigated properties confirm that XAnO₃ materials have FM-HM and high optical characteristics and they perfectly suitable for many spintronics and optoelectronics applications such as sensors, storage devices and photodiodes.