School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney, NSW 2006, Australia.
Phys Chem Chem Phys. 2019 Dec 4;21(47):25952-25961. doi: 10.1039/c9cp04325j.
The atomic order, electronic structure and thermodynamic stability of nickel aluminate, NiAl2O4, have been analyzed using periodic density functional theory and cluster expansion. NiAl2O4 forms a tetragonal structure with P4122 space group. At temperatures below 800 K, it is an inverse spinel, with Ni occupying the octahedral sites and Al occupying both the octahedral and the tetrahedral sites. Some Niocta + Altetra ⇌ Nitetra + Alocta exchange occurs above 800 K, but the structure remains largely inverse at high temperatures, with about 95% Niocta at 1500 K. Various functionals, with and without van der Waals corrections, were used to predict the experimental formation energy, lattice parameters and electronic structure. In all cases, the NiAl2O4 is found to be ferromagnetic and a semiconductor with an indirect band gap along the Γ → M symmetry points. NiAl2O4 is found to be thermodynamically stable at operating conditions of 900-1000 K and 1 atm relative to its competing oxide phases, NiO and Al2O3.
使用周期性密度泛函理论和团簇展开，分析了镍铝酸盐（NiAl2O4）的原子序、电子结构和热力学稳定性。NiAl2O4 具有 P4122 空间群的四方结构。在 800K 以下，它是反尖晶石，Ni 占据八面体位，Al 占据八面体和四面体位。在 800K 以上，会发生一些 Ni octa + Al tetra ⇌ Ni tetra + Al octa 交换，但在高温下结构仍主要为反尖晶石，在 1500K 时约有 95%的 Ni 占据八面体位。使用了各种具有和不具有范德华修正的泛函来预测实验形成能、晶格参数和电子结构。在所有情况下，NiAl2O4 被发现是铁磁半导体，具有沿 Γ→M 对称点的间接带隙。与竞争氧化物相 NiO 和 Al2O3 相比，NiAl2O4 在 900-1000K 和 1atm 的工作条件下是热力学稳定的。
