Gasphasengleichgewichte quaternärer Bismut‐Selen‐Oxidchloride

Gas‐Phase Equilibria of Quaternary Bismuth Selenium Oxidechlorides The existence of new compounds Bi₄O₄SeCl₂, Bi₁₀O₁₂SeCl₄, and Bi₂₂O₂₈SeCl₈ in the pseudoternary area Bi₂O₃/Bi₂Se₃/BiCl₃ has been established by solid state and chemical vapour transport reactions. Furthermore, heterogeneous equilibria between solid state and vapour phase have been studied by mass‐spectrometric measurements. The novel gas‐molecule BiSeCl has been detected. The results of ab initio calculations for structure and refining of thermochemistry of this molecule are given: (Bi–Se) = 2,44 Å; (Bi–Cl) = 2,49 Å; (Se–Bi–Cl) = 106,0°; Thermodynamics: δH°_B,298 (BiSeCl_g) = 6,0 kcal/mol; S°₂₉₈ (BiSeCl_g) = 75,8 cal/mol K; Cp (BiSeCl_g) = 13,583 + 0,64 · 10^–3 · T – 0,41 · 10⁵ · T^–2 – 0,35 · 10^–6 · T² cal/mol K. Finally, the composition of the gaseous phase has been calculated and estimations about chemical vapour transport were carried out by thermodynamic modelling.