High-pressure chemistry of nitrogen-rich compounds

当今材料科学和技术的关键方面是设计方法来生产可持续发展的新型材料，如环境友好型材料、储氢和储能材料、轻质和超硬材料等。在化学合成中应用极端条件，如高压和高温，使获得亚稳态和动能受阻化合物的新途径成为可能。氮化物是一类特别受益于加压的化合物，它不仅有助于稳定预期的经典氮化物，而且通过促进新的非典型化合物中同核N-N键和多氮物种的形成，极大地丰富了二元氮化物的化学组成。这些氮化物化合物的实际应用范围从超硬、不可压缩材料、发光二极管、铁电材料到高能量密度材料。然而，高压固态化学面临着几个根本性的挑战。首先，对于在50 Gpa以上的压力下发生的反应，几乎完全没有化学直觉，这是由缺乏系统的经验信息定义的。因此，目前氮气的高压化学主要由从头算结构预测方法主导，这些方法为新材料的实验实现提供了非常有价值的信息，但强烈需要独立的实验反馈。第二个挑战是，可以在传统的钻石顶压室中合成的样品的大小无法研究材料的所有属性，并限制了任何实际应用。因此，开发一种可扩展的高压合成新型非典型化合物是推动高压固相化学发展的关键一步。在这个项目中，我们专注于这两个挑战。首先，我们建议系统地研究氮与碱金属和碱土金属(离子聚氮化物)、主族元素(共价聚氮化物)和过渡金属(混合离子和共价化合物)反应中的高压化学。这将为增加三元和四元体系的结构和组成复杂性以及定向合成具有所需性能的材料(例如铁电氮化物钙钛矿)奠定坚实的基础。其次，我们将专注于开发可扩展的合成程序，使其能够获得新型高压材料的整体性能。这些技术进步不仅对氮化物化学，而且对整个高压固态化学领域都具有重要意义。

Key aspect of the material science and technology today is designing approaches for producing novel materials for sustainable development, such as environmentally friendly materials, materials for hydrogen and energy storage, lightweight and ultra-hard materials etc. Applying extreme conditions, such as high pressures and high temperatures, in chemical synthesis enables novel routes to metastable and kinetically hindered compounds. Nitrides are the class of compounds that especially benefit from the applications of pressure, which can help not only to stabilize expected classical nitrides but also to greatly enrich the chemistry of binary nitrides by promoting the formation of homonuclear N–N bonds and polynitrogen species in new atypical compounds. The practical use of these nitride compounds spans from ultrahard, incompressible materials, light-emitting diodes, ferroelectrics to high-energy density materials. However, the high-pressure solid-state chemistry faces several fundamental challenges. First one is almost complete absence of the chemical intuition for the reactions that occur at pressures above 50 GPa, that is defined by the lack of systematic empirical information. Therefore, nowadays, the high-pressure chemistry of nitrogen is dominated by the ab initio structure prediction methods, which provide very valuable information for the experimental realization of novel materials, but strongly require an independent experimental feedback. The second challenge is that the size of the sample, that could be synthesized in a conventional diamond anvil cell, does not allow studying all the properties of the material and limits any practical applications. Therefore, the development of a scalable high-pressure synthesis of novel atypical compounds is the essential step for the advancement of the high-pressure solid-state chemistry. In this project we concentrate on both challenges. First, we propose to systematically study the high-pressure chemistry of nitrogen in its reactions with alkali and alkaline-earth metals (ionic polynitrides), main-group elements (covalent polynitrides), and transition metals (mixed ionic and covalent compounds). This will build a solid basis for increasing the structural and compositional complexity in ternary and quaternary systems, as well as for the targeted synthesis of materials with desired properties (e.g. ferroelectric nitride perovskites). Secondly, we will focus on the development of scalable synthetic procedures that would allow getting access to the bulk properties of novel high-pressure materials. These technological advances will be of great importance not only for the chemistry of nitrides, but for the whole field of high-pressure solid-state chemistry.