Molecular structures and thermodynamic properties of 12 gaseous cesium-containing species of nuclear safety interest: Cs2, CsH, CsO, Cs2O, CsX, and Cs2X2 (X = OH, Cl, Br, and I)

Ab initio electronic structure calculations at the coupled cluster level with a correction for the triples extrapolated to the complete basis set limit have been made for the estimation of the thermochemical properties of Cs2, CsH, CsO, Cs2O, CsX, and Cs2X2 (X = OH, Cl, Br, and I). The standard enthalpies of formation and standard molar entropies at 298 K, and the temperature dependence of the heat capacities at constant pressure were evaluated. The calculated thermochemical properties are in good agreement with their literature counterparts. For Cs2, CsH, CsOH, Cs2(OH)2, CsCl, Cs2Cl2, CsBr, CsI, and Cs2I2, the calculated Δ f H 298 K ∘ values are within chemical accuracy of the most recent experimental values. Based on the excellent agreement observed between our calculated Δ f H 298 K ∘ values and their literature counterparts, the standard enthalpies of formation at 298 K are estimated to be the following: Δ f H 298 K ∘ (CsO) = 17.0 kJ mol−1 and Δ f H 298 K ∘ (Cs2Br2) = −575.4 kJ mol−1.