Department of Chemistry and Biochemistry, University of Maryland , College Park, Maryland 20742, United States.
Center for Nanophysics and Advanced Materials, University of Maryland , College Park, Maryland 20742, United States.
J Am Chem Soc. 2016 Dec 21;138(50):16432-16442. doi: 10.1021/jacs.6b10229. Epub 2016 Dec 9.
We present a general strategy to synthesize metastable layered materials via topochemical deintercalation of thermodynamically stable phases. Through kinetic control of the deintercalation reaction, we have prepared two hypothesized metastable compounds, CoSe and CoS, with the anti-PbO type structure from the starting compounds KCoSe and KCoS, respectively. Thermal stability, crystal structure from X-ray and neutron diffraction, magnetic susceptibility, magnetization, and electrical resistivity are studied for these new layered chalcogenides; both CoSe and CoS are found to be weak itinerant ferromagnets with Curie temperatures close to 10 K. Due to the weak van der Waals forces between the layers, CoSe is found to be a suitable host for further intercalation of guest species such as Li-ethylenediamine. From first-principles calculations, we explain why the Co chalcogenides are ferromagnets instead of superconductors as in their iron analogues. Bonding analysis of the calculated electronic density of states both explains their phase stability and predicts the limits of our deintercalation technique. Our results have broad implications for the rational design of new two-dimensional building blocks for functional materials.
我们提出了一种通过热力学稳定相的拓扑化学脱插来合成亚稳层状材料的通用策略。通过脱插反应的动力学控制，我们分别从起始化合物 KCoSe 和 KCoS 中制备了两种假设的亚稳化合物 CoSe 和 CoS，它们具有反-PbO 型结构。我们对这些新的层状硫族化物进行了热稳定性、X 射线和中子衍射晶体结构、磁化率、磁化强度和电阻率研究；发现 CoSe 和 CoS 都是弱巡游铁磁体，居里温度接近 10 K。由于层间的弱范德华力，CoSe 被发现是进一步插入客体物种（如 Li-乙二胺）的合适宿主。通过第一性原理计算，我们解释了为什么 Co 硫属化物是铁磁体而不是像它们的铁类似物那样的超导体。计算电子态密度的键合分析既解释了它们的相稳定性，也预测了我们脱插技术的极限。我们的结果对功能材料的新型二维构建块的合理设计具有广泛的意义。
