Molecular and ionic sublimation poly- and single crystals of gadolinium tribromide
The molecular and ionic sublimation of poly- and single crystals of gadolinium tribromide was studied in the Knudsen and Langmuir regimes. In the temperature range of 894 - 1044 K the monomer and dimer molecules and GdBr4- and Gd2Br7- negative ions were observed. The partial vapor pressure of neutral species were determined and the sublimation enthalpies (ΔsH°(298 K), kJ mol-1) in the form of monomer (296 ± 5) and dimer (384 ± 28) were obtained. The equilibrium constants of ion molecular reactions including GdBr4- and Gd2Br7- ions were measured and the reaction enthalpies were calculated. The enthalpies of formation (ΔfH°(298 K) kJ mol-1) of molecules - 542 ± 6 (GdBr3), -1292 ± 28 (Gd2Br6) and ions - 1070 ± 27 (GdBr4-) and - 1844 ± 50 (Gd2Br7-) are recommended.