Thermodynamic study of tin tetraiodide (SnI4) sublimation by effusion techniques

Abstract

This study presents the first investigation of the sublimation behavior of tin tetraiodide, SnI4, using effusion-based techniques, within a low temperature range (313–340) K. The temperature range covered in the experiments was lower than in previously reported studies based on static methods. Knudsen Effusion Mass Loss (KEML) measurements were performed in the range of (317.1–339.6) K using effusion cells with different orifice sizes. The vapor pressures were measured in the range (0.13–1.13) Pa and were found to be independent of the orifice size. The standard molar enthalpy and Gibbs energy of sublimation at 298.15 K obtained by the Clarke and Glew fit of experimental data are (88.1 ± 0.9) kJ⋅mol−1 and (38.96 ± 0.08) kJ⋅mol−1, respectively. Knudsen Effusion Mass Spectrometry (KEMS) experiments were also performed in the range (313.3–331.7) K, resulting in a sublimation enthalpy value in good agreement with the KEML values and not negligibly higher vapor pressure values. KEMS vapor pressure data were also analyzed by the third-law method. A comparison of our experimental results with the literature data available for both sublimation and evaporation properties of SnI4 is reported. Additionally, ancillary DFT and ab initio calculations were performed to estimate the molecular properties of SnI4(g) and the extent of the gas-phase dissociation to SnI2 and I2.