DFT analysis of rare-earth double perovskite oxides KXSn2O6 (X = Pr, Nd)

초록

In this study, we employ density functional theory (DFT) to investigate the structural, electronic, optical, elastic, magnetic, and thermal properties of rare-earth-based double perovskite oxides KXSn2O6 (X = Pr, Nd). Both compounds crystallize in the cubic Fm3 m space group, with optimized lattice constants of 8.243 & Aring; (KPrSn2O6) and 8.215 & Aring; (KNdSn2O6). Their structure comprises corner-sharing SnO6 octahedra and A-site Pr/Nd ions forming mixed ionic-covalent bonds. Negative formation energy, phonon dispersion, and the Birch-Murnaghan equation of state confirm structural stability. Electronic band structures using the mBJ potential show spin-polarized indirect semiconducting gaps of 2.095 eV (Pr) and 2.374 eV (Nd) in the spin-down channel. The valence band is dominated by O-2p states, while conduction bands involve Sn-5p/5d and Pr/Nd-4f orbitals, suggesting optoelectronic and spintronic utility. Strong UV absorption begins at 2.2-2.5 eV, with absorption peaks in the range of 6 eV-13 eV KPrSn2O6 exhibits higher optical constants (n ti 6.6, R ti 68 %) than KNdSn2O6 (n ti 1.9, R ti 45 %). Elastic constants validate mechanical stability, with Young's moduli of 280 GPa (Pr) and 270 GPa (Nd), and Pugh's ratios indicating ductility. Magnetic analysis reveals total moments of 2.00 mu B (Pr) and 2.99 mu B (Nd), mainly from rare-earth 4f-electrons. Thermal assessments show Debye temperatures of 581 K (Pr) and 567 K (Nd), indicating strong lattice stiffness and high melting points. These findings highlight KXSn2O6 as a promising multifunctional candidate for UV optoelectronics, spintronics, and high-temperature electronics.

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