Mischkristalle aus A4B3-Molekülen (A = P,As; B = S,Se)

Mixed Crystals from A₄B₃ Molecules (A = P, As; B = S, Se) The system P₄S₃? P₄Se₃? As₄S₃? As₄Se₃ was investigated by thermal and x-ray methods. Five regions of solid solubility with different crystal structures were found at room temperature. The range of existence can be influenced by the temperature of annealing. All these phases transform into a plastic-crystalline modification with complete solid solubility at higher temperature. A decomposition reaction of the A₄B₃ molecules was observed in the P₄Se₃/As₄Se₃/As₄S₃ part of the system. The molecules decompose into A₄B₄ molecules and an amorphous phase. The existence of all molecules of the type P_nAs_4–nS_mSe_3–m (n = 0–4, m = 0–3) and also As₄S_mSe_4–m (m = 1–3) was verified by mass spectrometric measurements. The thermochemical data of the mixed crystals are determined by the type of the constituent A₄B₃ molecules. The temperature and the entropy of the α–β transition are lower for mixed crystals, formed by substituted molecules, than for those of the same structure, consisting of pure A₄B₃ molecules.