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

在广泛而系统的方法中，结合合成和计算方法，我们的目标是合成和结构研究新的和迄今为止未知的三元或更高的硝基硅酸盐和氧硝基硅酸盐（离子）的高压相。线的制备过程将使用我们内部的沃克式多砧技术和激光加热的金刚石砧细胞，而实验将采用密度泛函理论方法进行理论研究。所研究的材料在结构上与经典（氧）硅酸盐和二元高性能陶瓷（如Si3N4或AlN）相关。与已知的高压氧硅酸盐（如辉石）类似，新的高压化合物有望表现出前所未有的晶体结构（凝聚的SiN6八面体甚至SiN5单元）。这将导致卓越的微观和宏观材料性能（如硬度，体模量，固态核磁共振化学位移，光学性能），将被研究。计算将提前进行，以确定高压转换的候选者，并阐明可能的过渡路径。之后，计算性质（晶格参数和高压下的振动谱，核磁共振化学位移）将证实实验表征的结果。在各自的相图中，对新相的结构稳定性和热力学关系将有一个全面的了解。

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.