Computational Chemistry Derivation of Cr, Mn, and La Hydroxide and Oxyhydroxide Thermodynamics

Thermodynamic quantities are calculated for gaseous hydroxides and oxyhydroxides of Cr, Mn, and La. These would form due to water-vapor-containing environments reacting with Cr-forming alloys or oxide components of potential fuel cell interconnects or anode materials. Structures and vibrational modes for the expected hydroxides and oxyhydroxides are calculated with the B3LYP hybrid functional. Enthalpies of formation from selected reactions for each species are calculated using the CCSD(T)/CBS approach. Results show good agreement with literature estimates, measurements, and calculations. The resultant data is reported as Δ_fH°(298), S°(298), and C_p(T) and put into the database for a free-energy minimizer code. Calculations are presented to show the hydroxide and oxyhydroxide vapor pressures above H₂O + Cr₂O₃, Mn₃O₄, and La₂O₃, as well as the anode material La_0.75Sr_0.25Cr_0.5Mn_0.5O_3-δ (LSCM).