High-pressure investigations on binary and ternary acetylides

该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）预计将于2021年底在科隆大学投入使用，将用于此目的。该项目的目的是合成所谓的多碳化物，这已经在理论工作的基础上预测了近10年，以毫克的数量，并进行详细的结构表征。由于预测这些多碳化物具有有趣的性质，例如超导性，因此这些化合物的特征也应该超出纯结构分析（例如电导率测量）。在迄今为止所描述的调查中，几乎完全使用金刚石砧座单元，其仅允许（部分有限的）原位表征。此外，在大多数实验中不使用加热，这就是为什么由于推测的动力学抑制而不能获得结晶产物的原因。使用上述LVP应该克服这些限制，因为加热到1500 °C以上的温度（15 GPa）是可能的，并且可以获得mg数量的产品以进行进一步的研究。迄今为止的所有研究都表明，聚碳化物在减压到环境压力后是亚稳态的。这些实验是与Häussermann和Kohlmann小组（分别位于斯德哥尔摩和莱比锡）合作进行的，他们正在汉堡Petra III同步加速器上建立一个用于现场高压实验的测量台，作为X射线埃簇项目的一部分。这些补充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，它们还允许检测在LVP中减压后将再次分解的产物。除了对多碳化物的研究之外，这将为碳（金刚石，石墨，富勒烯，碳纳米管，石墨烯）已经非常丰富的结构化学增加另一个有趣的方面，我们希望使用上述设置来研究碳（石墨）的氧化能力如何在压力下变化。对于其他主族元素，包括氢，已经表明在压力下元素铂氧化至+4氧化态是可能的。对碳的类似研究尚不清楚。但是对于我们不久前合成的三元乙炔化物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.