Bulk And Surface Properties Of Spinel Co_3o_4 By Density Functional Calculations

摘要

DFT calculations are employed to bulk and surface properties of spinel oxide Co_3O_4. The bulk magnetic structure is calculated to be antiferromagnetic, with a Co~(2+) moment of 2.631μ_B in the antiferromagnetic state. There are three predicted electron transitions O(2p)→ Co~(2+)(t_(2g)) of 2.2 eV, O(2p) → Co~(3+)(e_g) of 2.9 eV and Co~(3+)(t_(2g))→ Co~(2+)(t_(2g)) of 3.3 eV, and the former two transitions are close to the corresponding experimental values 2.8 and 2.4 eV. The naturally occurring Co_3O_4 (110) and (111) surfaces were considered for surface calculations. For ideal CO_3O-4 (110) surfaces, the surface relaxations are not significant, while for ideal Co_3O_4 (111) surfaces the relaxation of Co~(2+) cations in the tetrahedral sites is drastic, which agrees with the experiment observation. The stability over different oxygen environments for possible ideal and defect surface terminations were explored.