High-pressure synthesis of novel transition metal polynitrides

近年来，氮气的高压化学在几个突破性的发现后成为研究的热点：在高压高温条件下合成碱土金属二叠氮化物、过渡金属过氮化物和多聚氮同素异形体CG-N。在压力的作用下，通过简单的反应M+1/2 x N_2-&gt；MN_x，可以直接合成具有共价N-N键的新型无机材料，其中M可以是元素周期表中的几乎任何元素。理论计算预测了100多种聚氮化物，它们可能具有高硬度、低压缩率、高能量密度等重要的化学和物理性能，但到目前为止，实验信息非常有限。该项目的目标是系统地研究过渡金属聚氮化物(重点是Re、Os、W、Cr、Ru、Ti、Zr、Hf)在高压-高温条件下的形成，并研究其晶体化学和物理性质。在本项目中，聚氮化物将在激光加热的金刚石顶压室中通过金属和氮的直接反应在高压和高温下合成。我们通常所说的“多氮化物”或“多氮化合物”指的是由氮原子构成的含有聚合链和低聚链、环结构或3D网络的化合物。我们将利用一系列先进的辅助技术对所得到的材料进行研究：单晶X射线衍射(XRD)、拉曼光谱、FIB辅助分析回收材料和理论计算。该项目的最终目的是揭示不同金属聚氮化物的合成条件、化学键、结构和性能之间的关系，并制定控制极端条件下聚氮化物形成和行为的晶体化学原理。

The high-pressure chemistry of nitrogen became a hot topic in the recent years after several breakthrough discoveries: the synthesis of alkali earth metal diazenides, transition metal pernitrides, and polymeric nitrogen allotrope cg-N at high-pressure high-temperature conditions. An application of pressure opens a straightforward synthetic route to new inorganic materials with covalent N-N bonds through the simple reaction M + 1/2 x N2 -> MNx, where M can be almost any element from the periodic table. Theoretical calculations predict over a hundred of polynitrides that may have important chemical and physical properties like high hardness, low compressibility, high energy density etc., however up to now the experimental information is very limited. The goal of the project is the systematic study the formation of transition metal polynitrides (with focus on Re, Os, W, Cr, Ru, Ti, Zr, Hf) at high-pressure-high temperature conditions, and study their crystal chemistry and physical properties. In the present project, polynitrides will be synthesized at high pressures and temperatures in laser-heated diamond anvil cells in a direct reaction between metal and nitrogen. By the common term “polynitrides” or “polynitrogen compounds” we mean compounds containing polymeric and oligomeric chains, ring structures, or 3D networks, built from nitrogen atoms. The resulting materials will be studied employing a range of advanced complimentary techniques: single-crystal X-ray diffraction (XRD), Raman spectroscopy, FIB-assisted analysis of recovered materials, and theoretical calculations. The ultimate aim of the project is to reveal relations between synthetic conditions, chemical bonding, structure, and properties of polynitrides of different metals, and to formulate crystal chemical principals governing formation and behavior of polynitrides at extreme conditions.