Knudsen measurements of the sublimation and the heat of formation of GeSe 2 [1]

Knudsen effusion studies of the sublimation of polycrystalline GeSe 2 have been performed employing mass spectrometry in a temperature range of about 610–750 K and vacuum microbalance techniques in the temperature range 614–801 K and at pressures ranging from about 10 −7 − 10 −4 atm. The results demonstrate that GeSe 2 vaporizes congruently under present experimental conditions according to the predominant reaction (1) GeSe 2 (s) = GeSe(g) + 1/2 Se 2 (g) and a minor reaction (2) GeSe 2 (s) = GeSe 2 (g). The mean values for the third law heat and second law entropy of reaction (1) based on direct mass‐loss data are ΔH° 298 = 70.4 ± 2 kcal/mole and ΔS° 298 = 64.7 ± 2 eu. From these the standard heat of formation and absolute entropy of GeSe 2 (s) were calculated to be −21.7 ± 2 kcal/mole and 24.6 ± 2 eu, respectively.