Density Functional Study of Chromium Oxide Clusters:  Structures, Bonding, Vibrations, and Stability

Abstract

We report the results of density functional theory calculations on chromium oxide clusters responding to the formula Cr m O n (m ) 1-2, n ) 1-3). Double numeric basis sets supplemented by polarization functions have been used in both local and nonlocal spin density approximations. Geometry optimizations of different spin states have been performed at the unrestricted spin level for the selected initial configurations. We have found that the covalent polarized Cr-O bonds dominate the chemical description of the CrO n series, while for the Cr 2 O n series the presence of the Cr-Cr bond reduces the metal to oxygen charge transfer, yielding much softer clusters, as reflected by the smaller HOMO-LUMO gaps. The stability of all the isomers has been checked by computing their harmonic vibrational frequencies and the energetics of different fragmentation paths. The calculations reveal that the linear isomers are not true minima and that the oxygen-rich clusters are preferred over the metal-rich clusters. Overall, our results show good agreement with the available experimental data in terms of geometrical parameters, vibrational frequencies, atomization energies, and fragmentations for the CrO n clusters. For the Cr 2 O series, our computed values are discussed in connection with recent infrared spectroscopy measurements and with available data in analogous metal oxide clusters.

Calculation of Reactive-evaporation Rates of Chromia

“…The value of 1.6×10 -10 m comes from a density functional theory estimation of the length of a Cr-O bond in CrO. 11 The values of v i for the mixtures other than air were based on a weighted average of the component v i values.…”

How Cr2O3 influences the microstructure and nonohmic features of the SnO2(Cox, Mn1−x)O-based varistor system

“…In their theoretical calculation of chromium oxide clusters, Veliah et al 41 found that CrO n -type clusters are more stable than Cr m O n -type clusters. The CrO n -type clusters presented Cr O bonds with covalent and polar features.…”

Magnetic properties of Cr2On− clusters: A theoretical study

“…Chromium oxide clusters, both neutral and anionic, have been a topic of current research interest [8][9][10][11][12][13][14]. Different properties of neutral chromium oxide clusters have been correlated with electronic structure by Pandey and coworkers [8].…”

“…Different properties of neutral chromium oxide clusters have been correlated with electronic structure by Pandey and coworkers [8]. Whereas, the variation of their electronic structure as well as the magnetic property as a function of oxidation and composition have been discussed by Zhai and Wang [9] and Reddy and Khanna [10], respectively.…”