Spin-polarized DFT calculations were performed using the projector augmented wave (PAW) potential method implemented in the Vienna Ab Initio Simulation Package (VASP) code . Generalized gradient approximation (GGA) within the scheme of Perdew-Burke-Ernzerhof (PBE) was used as the basis of the exchange-correlation (XC) functional. The Hubbard U correction proposed by Dudarev et al. with the following U values was applied, respectively, for Sc, Mn, and Ni to compute the atomistic structures: 5.0 eV, 5.2 eV, and 6.8. The dispersion D3 correction was added for the low Na concentration. We applied the Heyd-Scuseria-Ernzerhof (HSE06) functional to compute the electronic structure (i.e. number of unpaired electrons (Nunp) on elements and spin density). The Gamma-centered k-point mesh of 2×2×2 and an energy cut off of 550 eV as well as an electronic and a force convergence criterion of 10 -4 eV and -2.00*10 -2 eV/Å, respectively, were used for DFT calculations. Magnetic moments (number of unpaired electrons) were calculated using a tighter electronic and force convergence criterion of 10 -6 eV and 10 -5 eV/Å, respectively. Total Coulomb energy calculations on possible combinations were carried out using the so-called supercell code .