Thermochemistry of the Chromium Hydroxides Cr(OH)<i>_n</i>, <i>n</i> = 2−6, and the Oxyhydroxide CrO(OH)₄: Ab Initio Predictions

We here present a high-level ab initio study of the thermochemistry of the chromium hydroxides Cr(OH)n, n = 2−6, and of the oxyhydroxide CrO(OH)4. Optimum geometries and harmonic vibrational frequencies were determined at the B3LYP level of theory using basis sets of triple-ζ quality including polarization and diffuse functions. Heats of formation were obtained from isogyric reaction energies computed at the CCSD(T) level of theory using large basis sets and including corrections for core-valence correlation, scalar relativistic effects, and basis set incompleteness. Additionally, polynomial fits were performed for the heat capacity and the standard enthalpy and entropy over the 100−3000 K temperature range. While our computed heats of formation agree well with previously obtained experimental data for some of these species, our results suggest that revision of the experimental data for others may be appropriate.