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Effect of surrounding point charges on the density functional calculations of Ni x O x clusters ( x = 4–12)
Author(s) -
Kadossov Evgueni B.,
Gaskell Karen J.,
Langell Marjorie A.
Publication year - 2007
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.20669
Subject(s) - cluster (spacecraft) , atomic orbital , chemistry , ionic bonding , fermi level , atomic physics , charge (physics) , madelung constant , charge density , valence (chemistry) , x ray photoelectron spectroscopy , electronic structure , molecular physics , condensed matter physics , physics , ion , crystallography , computational chemistry , electron , lattice energy , nuclear magnetic resonance , crystal structure , quantum mechanics , organic chemistry , computer science , programming language
Embedded Ni x O x clusters ( x = 4–12) have been studied by the density‐functional method using compensating point charges of variable magnitude to calculate the ionic charge, bulk modulus, and lattice binding energy. The computations were found to be strongly dependent on the value of the surrounding point charge array and an optimum value could be found by choosing the point charge to reproduce the experimentally observed NiO lattice parameter. This simple, empirical method yields a good match between computed and experimental data, and even small variation from the optimum point charge value produces significant deviation between computed and measured bulk physical parameters. The optimum point charge value depends on the cluster size, but in all cases is significantly less than ±2.0, the formal oxidation state typically employed in cluster modeling of NiO bulk and surface properties. The electronic structure calculated with the optimized point charge magnitude is in general agreement with literature photoemission and XPS data and agrees with the presently accepted picture of the valence band as containing charge‐transfer insulator characteristics. The orbital population near the Fermi level does not depend on the cluster size and is characterized by hybridized Ni 3d and O 2p orbitals with relative oxygen contribution of about 70%. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007