High-pressure investigations on binary and ternary acetylides

本项目的重点是二元和三元乙炔的高压研究。最近批准的大容量印刷机(LVP)将用于这一目的，预计将于2021年底在科隆大学提供。该项目的目的是合成所谓的多碳化物，这种碳化物在理论工作的基础上已经预测了近10年，并以镁为数量，并进行详细的结构表征。由于这些多碳化物具有有趣的性质，例如超导电性，因此这些化合物的特征也不应仅限于纯结构分析(例如电导率测量)。在到目前为止所描述的研究中，几乎完全使用了钻石砧座单元，这只允许(部分有限的)原位表征。此外，在大多数实验中没有使用加热，这就是为什么由于动力学抑制而无法获得结晶产物的原因。上述LVP应克服这些限制，因为可以加热到1500°C以上的温度(在15 Gpa下)，并且可以获得产品的镁含量，以便进行进一步的研究。到目前为止的所有研究都表明，多碳化物在常压下减压后是亚稳定的。这些实验是与豪瑟曼和科尔曼小组(分别是斯德哥尔摩和莱比锡)合作进行的，这两个小组正在为现场高压实验建立一个测量台，这是汉堡Petra III同步加速器X射线角星团项目的一部分。这些互补的测量将理想地提供导致在LVP中成功合成的实验参数(压力、温度)。此外，它们还可以检测到减压后会再次分解的产品。除了对多碳化物的研究，这将为已经非常丰富的碳(钻石、石墨、富勒烯、碳纳米管、石墨烯)的结构化学增加另一个有趣的方面，我们想要使用上述装置来研究碳(石墨)在压力下的氧化能力如何变化。对于其他主要族元素，包括氢，已经表明元素铂在加压下可以氧化到+4氧化态。对碳的类似研究尚不清楚。但对于我们一段时间前合成的三元乙酰化合物Na2PdC2和Na2PtC2，理想的起始化合物将可用于这些研究。

This project focuses on high-pressure investigations of binary and ternary acetylides. A recently approved large-volume press (LVP), which is expected to be available at the University of Cologne at the end of 2021, will be used for this purpose. The aim of the project is to synthesise so-called polycarbides, which have already been predicted for almost 10 years on the basis of theoretical work, in mg quantities and to carry out a detailed structural characterisation. Since interesting properties, e.g. superconductivity, are predicted for these polycarbides, these compounds shall also be characterised beyond pure structural analysis (e.g. conductivity measurements). In investigations described so far, diamond anvil cells have been used almost exclusively, which only allow (partly limited) in-situ characterisation. In addition, heating was not used in most experiments, which is why no crystalline products could be obtained due to presumably kinetic inhibitions. These limitations should be overcome with the above-mentioned LVP, as both heating to temperatures above 1500 °C is possible (at 15 GPa) and mg quantities of the products can be obtained to enable further investigations. All investigations so far indicate that the polycarbides are metastable after decompression to ambient pressure.These experiments are accompanied by a cooperation with the Häussermann and Kohlmann groups (Stockholm and Leipzig, respectively), who are setting up a measuring stand for in-situ high-pressure experiments as part of an X-ray angstrom cluster project at the Petra III synchrotron in Hamburg. These complementary measurements would ideally provide the experimental parameters (pressure, temperature) that lead to successful syntheses in the LVP. Moreover, they would also allow the detection of products that would decompose again after decompression in the LVP.In addition to the studies on polycarbides, which would add another interesting facet to the already very rich structural chemistry of carbon (diamond, graphite, fullerenes, carbon nanotubes, graphene), we want to use the aforementioned setup to investigate how the oxidation power of carbon (graphite) changes under pressure. For other main group elements, including hydrogen, it has already been shown that oxidation of elemental platinum up to the +4 oxidation state is possible under pressure. Analogous investigations for carbon are unknown. But with the ternary acetylides Na2PdC2 and Na2PtC2, which we synthesised some time ago, ideal starting compounds would be available for these investigations.