Abstract Thermodynamic parameters are reported for gaseous hydroxides and oxyhydroxides of Al, Zr, and Y. The structures and vibrational frequencies are calculated using density functional theory with the B3LYP functional. This yields entropies at 298.15 K and heat capacities. The enthalpies are calculated from appropriate reactions and the CCSD(T) (Coupled Cluster, Singles, Doubles, and perturbative Triples) approach. The hydroxide groups are treated as hindered rotors for all species. The results are compared to the limited experimental and theoretical calculations for these species. Finally, the data are put into a database for a free‐energy minimizer and the vapor pressures for each species are compared.