Electronic structure, magnetic properties, and mixed valence character of Ce₂ Ni₃ Si₅ from first principles...

Cerium intermetallic compounds exhibit anomalous physical properties such as heavy fermion and Kondo behaviors. Here, an ab initio study of the electronic structure, magnetic properties, and mixed valence character of Ce₂ Ni₃ Si₅ using density functional theory (DFT) is presented. Two theoretical methods, including pure Perdew-Burke-Ernzerhof (PBE) and PBE + U, are used. In this study, Ce³⁺ and Ce⁴⁺ are considered as two different constituents in the unit cell. The formation energy calculations on the DFT level propose that Ce is in a stable mixed valence of 3.379 at 0 K. The calculated electronic structure shows that Ce₂ Ni₃ Si₅ is a metallic compound with a contribution at the Fermi level from Ce 4f and Ni 3d states. With the inclusion of the effective Hubbard parameter (U_eff ), the five valence electrons of 5 Ce³⁺ ions are distributed only on Ce³⁺ 4f orbitals. Therefore, the occupied Ce³⁺ 4f band is located in the valence band (VB) while Ce⁴⁺ 4f orbitals are empty and Located at the Fermi level. The calculated magnetic moment in Ce₂ Ni₃ Si₅ is only due to cerium (Ce³⁺ ) in good agreement with the experimental results. The U_eff value of 5.4 eV provides a reasonable magnetic moment of 0.981 μB for the unpaired electron per Ce³⁺ ion. These results may serve as a guide for studying present mixed valence cerium-based compounds. © 2017 Wiley Periodicals, Inc.