High-Pressure Nitridosilicates, Oxonitridosilicates and Nitridophosphates and Related Binary Nitrides

在一个广泛和系统的方法，结合合成和计算方法，我们的目标是合成和结构研究的新的和迄今未知的高压相的三元或更高的氮硅酸盐和oxonitridosilicates（sions）。线的制备过程将使用我们自己的沃克型多砧技术和激光加热金刚石对顶砧，而实验将通过理论研究，使用密度泛函理论方法进行验证。所研究的材料在结构上与经典的（氧代）硅酸盐和二元高性能陶瓷（如Si3N4或AlN）相关。类似于已知的高压氧硅酸盐（例如，硅镁石），新的高压化合物预计将表现出前所未有的晶体结构（凝聚的SiN6八面体或甚至SiN5单元）。这将导致突出的微观和宏观材料特性（例如硬度，体积模量，固态NMR化学位移，光学特性），将进行研究。计算将提前进行，以确定高压转换的候选人，并阐明可能的过渡路径。后，计算的性质（晶格参数和振动光谱在高压下，NMR化学位移）将证实实验表征的结果。在各自的相图中，将实现对新相的结构稳定性和热力学关系的全面理解。

Within a broad and systematic approach, combining both synthetical and computational methods, we are targeting synthesis and structural investigation of novel and hitherto unknown high-pressure phases of ternary or higher nitridosilicates and oxonitridosilicates (sions). The preparative course of line will use our in-house Walker-type multianvil technique and laser-heated diamond anvil cells, while experiments will be paralleled by theoretical studies using density functional theory methods. The materials under investigation are structurally related to both classical (oxo)silicates and binary high-performance ceramics such as Si3N4 or AlN. In analogy with known high-pressure oxosilicates (e.g. stishovite), the new high-pressure compounds are expected to exhibit unprecedented crystal structures (condensed SiN6 octahedrons or even SiN5 units). This will result in outstanding micro- and macroscopic materials properties (e.g. hardness, bulk moduli, solid-state NMR chemical shifts, optical properties) which will be investigated. Computations will be carried out in advance to identify candidates for high-pressure transformations and to elucidate possible transition paths. Posterior, computations of properties (lattice parameter and vibrational spectra at high pressures, NMR chemical shifts) will corroborate results of experimental characterizations. A comprehensive understanding of structural stability and thermodynamic relation of the new phases within their respective phase diagrams will be achieved.