Atomic order, electronic structure and thermodynamic stability of nickel aluminate. Issue 47 (4th October 2019)

• Record Type: Journal Article
• Authors: Elias, Ishfaque; Soon, Aloysius; Huang, Jun; S. Haynes, Brian; Montoya, Alejandro
• Is Part Of: Physical chemistry chemical physics. Volume 21:Issue 47(2019)
• Page Start: 25952
• Page End: 25961
• Publication Date: 2019-10-04
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c9cp04325j
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Nickel aluminate, NiAl2 O4, adopts the inverse tetragonal P 41 22 structure and remains largely inverse below 1000 K. Abstract : The atomic order, electronic structure and thermodynamic stability of nickel aluminate, NiAl2 O4, have been analyzed using periodic density functional theory and cluster expansion. NiAl2 O4 forms a tetragonal structure with P 41 22 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 Ni octa + Al tetra ⇌ Ni tetra + Al octa exchange occurs above 800 K, but the structure remains largely inverse at high temperatures, with about 95% Ni octa 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 NiAl2 O4 is found to be ferromagnetic and a semiconductor with an indirect band gap along the Γ → M symmetry points. NiAl2 O4 is found to be thermodynamically stable at operating conditions of 900–1000 K and 1 atm relative to its competing oxide phases, NiO and Al2 O3 .