Effect of exchange and correlation on bulk properties of MgO, NiO, and CoO

Abstract

Bulk properties of the isostructural oxides MgO, NiO, and CoO have been calculated quantum chemically with periodic models and compared with experimental data from the literature. Ab initio Hartree-Fock, gradient-corrected density-functional methods, and hybrid approaches have been used for the calculation of the lattice constants, heats of atomization, and electronic structures. General trends of the effects of electron correlation and the treatment of exchange on the calculated properties are observed. None of the standard methods considered provided results in agreement with experimental data for all properties. A combination of Becke's three-parameter exchange functional and the Lee-Yang-Parr correlation functional (B3LYP) leads to a consistent description of the electronic and structural properties in comparative studies of the three compounds. Other methods are more accurate than B3LYP if certain properties or compounds are considered. The combination of the Hartree-Fock exchange functional with the Lee-Yang-Parr density-functional correlation is the best method for the open-shell transition-metal oxides NiO and CoO in terms of relative stability and geometry and the electronic structure of the valence band. The absolute values of calculated heats of atomization, however, are generally too small. The density-functional method based on the Perdew-Wang generalized gradient approximation (PWGGA) is preferable for the calculation of thermodynamic properties for all compounds but is less reliable in the prediction of structural and electronic properties. A hybrid approach based on the PWGGA method is proposed that improves the results for bulk geometries and electronic properties while maintaining the high quality of calculated energetic results.

Keywords

Affiliated Institutions

• University of South Australia AU

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