ERA-Chemistry: Searching for ultra-incompressible materials: Formation and characterisation of binary and ternary period 6 transition metal borides at very high pressures and temperatures

有针对性地寻找超不可压缩化合物的一种方法是基于这样一种思想，即高价电子密度与共价键的结合应该为化合物提供所需的性质。这导致了对含有6周期重过渡金属离子（Ta，W,Re,Os,Ir）和轻元素（如碳，氮或硼）的化合物的广泛搜索。其中一些化合物，如OsB2，确实表现出了突出的物理性质，但一些被认为很有前途的化合物，如B:Re比为bbb20的硼化铼，还没有被合成。众所周知，高压/高温条件可能导致不寻常的键合环境和新的结构类型。然而，我们对二元周期6过渡金属硼化物的高压行为的了解相当有限。虽然相应的碳化物和氮化物已经得到了很好的研究，但在极端p， t条件下的原位合成硼化物的研究尚未发表，因此我们对二元和三元周期6过渡金属硼化物的p， t相稳定性的了解非常有限。因此，目前的建议侧重于了解在非常高的压力和温度下在激光加热的金刚石顶孔和大体积高压装置中获得的二元和三元6过渡金属硼化物的相关系、结构和性质，并辅之以高速球磨机械化学激活合成和基于密度泛函理论的原子模型计算。样品将通过多种技术进行表征，包括微量热法、振动光谱和同位素富集化合物的中子衍射。该项目充分利用了因斯布鲁克和法兰克福的互补专业知识和可用的实验设备，并有望产生新的化合物，更深入地了解硼化物的晶体化学，并可能合成具有优异性能的材料。

One approach for the directed search for ultra-incompressible compounds is based on the idea that acombination of a high valence electron density in conjunction with covalent bonds should providecompounds with the desired properties. This has led to an extensive search for compounds containingheavy transition metal ions of period 6 (Ta,W,Re,Os,Ir) and a light element, such as carbon, nitrogen orboron. Some of these compounds, such as OsB2, have indeed shown outstanding physical properties, but several compounds, which are thought to be very promising, such as a rhenium boride with a B:Re ratio > 2, have not been synthesized yet. It is well established that high pressure/high temperature conditions may lead to unusual bonding environments and new structure types. However, our knowledge of the high pressure behavior of binary period 6 transition metal borides is rather limited. While the corresponding carbides and nitrides are well investigated, no in-situ synthesis studies of borides at extreme p,T-conditions have been published yet and hence our knowledge of the p,T-phase stabilities of binary and ternary period 6 transition metal borides is extremely limited. Hence, the current proposal focusses on understanding phase-relations, structures and properties of binary and ternary period 6 transition metal borides obtained at very high pressures and temperatures in laser heated diamond anvil cells and large-volume high pressure devices, complemented by mechanochemically activated synthesis with high speed ball milling and density functional theory based atomistic model calculations. Samples will be characterized by numerous techniques, including microcalorimetry, vibrational spectroscopy and neutron diffraction on isotopically enriched compounds. The project fully exploits the complementary expertise and available experimental equipment in Innsbruck and Frankfurt and promises to yield novel compounds, a deeper understanding of the crystal chemistry of borides and possibly a route to synthesize materials with outstanding properties.