Phase relations and kinetics of phase formation of non-equilibrium-solids of pnicogens and chalcogens - Mechanisms of structure formation, synthesis and characterization of element allotropes and compounds -

在这个项目中，EnPhaSys-concept总结了不同的方法：量子化学建模和确定所研究系统的能量景观，相形成分析和无机固体合成。这一概念被应用于确定亚稳相和稳定相的热力学关系、同素异形体和产烟素和产硫素化合物的相形成和转变动力学以及非平衡相的成核和种子生长过程。拟开展三个子课题：A)磷、砷同素异形体的相形成与转化机理；利用原位核磁共振、原位中子衍射和气相分析研究成核和种子生长过程。该部分项目将充分阐明磷和砷元素同素异形体的热力学关系。描述了同素异形体的相形成和转变机理，并阐明了矿化效应。通过时间依赖性相形成动力学的补充研究，等温压力测量，固相和气相核磁共振波谱，以及晶体相生长的粉末中子衍射，为确定形成机制以及同素异形体的成核和种子生长过程提供了信息。B)具有多阴离子相MX2和MXY （X, Y = P, As, Se, Te）多态性的亚稳态和稳定候选物的鉴定及其定向合成的有序现象，从而研究由哑铃型X-X和X-Y组成的多阴离子亚结构的二元和三元化合物MX2和MXY的多态性关系。通过使用EnPhaSyn概念，有可能根据热力学稳定性对多晶相进行排序，并根据不同的相稳定性以系统的方式指导合成。c)三元金属间LAVES相有序-无序现象的研究；有序相、部分有序相和无序相稳定性判据的确定定向合成LAVES相通常存在，组分随机分布，因此表现出明显的无序性。除了这些明显稳定的相之外，还可以想象出大量不同组成的有序化合物。确定它们的稳定性和分析相形成是该项目的目的。基于EnPhaSyn概念发现有序LAVES相的新代表A4B7B′，将合成更多有序亚稳过渡金属-砷化合物。比较了不同阶序相定向生长的稳定性和条件。

In this project, different methods are summarized in the EnPhaSys-concept: quantum chemical modeling and determination of the energy landscape of investigated systems, analysis of phase formation, and inorganic solid state synthesis. This concept is applied to determine the thermodynamic relations of metastable and stable phases, the kinetics of phase formation and transformation of allotropes and compounds of pnicogenes and chalcogenes, and the processes of nucleation and seed growth of the non-equilibrium phases.Three sub-projects are to be processed:A) Mechanisms of phase formation and transformation of allotropes of Phosphorus and Arsenic; investigation of nucleation and seed growth processes by using in-situ-NMR, in-situ-neutron diffraction, and gas phase analysisThis partial project shall fully clarify the thermodynamic relations of allotropes of the elements phosphorus and arsenic. The mechanisms of phase formation and transformation of allotropes are to describe, and the effect of mineralization is to elucidate. Complementary investigations of the kinetics of phase formation by time dependent, isothermal pressure measurements, solid state and gas phase NMR spectroscopy, and powder neutron diffraction of the crystalline phases growth supply information on the identification of formation mechanism and on the nucleation and seed growth processes of the allotropes.B) Identification of metastable and stable candidates showing polymorphism of polyanionic phases MX2 and MXY (X, Y = P, As, Se, Te) and their directed synthesisOrdering phenomena and thus the relations of polymorphism of binary and ternary compounds MX2 and MXY consisting of polyanionic substructures with dumbbells X-X and X-Y shall be investigated. By using the EnPhaSyn concept there is the potential of ordering the polymorphic phases by thermodynamic stability and directing the synthesis in a systematic way depending on different phase stabilities.C) Investigation of order-disorder phenomena of ternary intermetallic LAVES phases; determination of stability criteria of ordered, partially ordered, and disordered phases; directed synthesisTernary LAVES phases commonly exist with random distribution of components and therefore show distinct disordering. Besides these obviously stable phases a plethora of ordered compounds of various compositions is conceivable. It is aim of the project to determine their stabilities and to analyze the phase formation. Based on the discovery of the new representative of ordered LAVES phases, A4B7B‘, by the EnPhaSyn concept, more ordered metastable transition metal - arsenic compounds shall be synthesized. A comparison of the stabilities and the conditions for directed growth of phases of different ordering is intended.