含阴离子共价键X-X基元（X=As，Se和Te）化合物的结构设计和物性调控

In the novel superconducting and electromagnetic compounds discovered in the last a few years, there are many kinds of charge-reservoir units composed of anionic covalent bonds, such as the zigzag chain of -As--As--bonds, the dimer of [Se-Se]2-, the square net of Bi2- etc, except the common quasi-two dimensional [La2O2]2+和[Ca2F2]2+ layers. As tuning the stoichiometry or isovalent substitution, it could lead to the distortion of covalent charge-reservoir units and releasing or transferring of electrons, which would effectively control the electron concentrations and realize ‘self-doping’ in compounds. Based on the previous work, this project focuses on the binary or multicomponent compounds with transition metals Tm (Tm = W, Fe, Co, Rh and Ir) and X (X = As, Se and Te) to design new type of charge-reservoir units with anionic bonds (X-X). It is proposed to use chemical substitution and doping to distort the structural unit, and then characterize its effect on change of electron concentrations. The main target is exploring the novel superconducting and electromagnetic properties induced by distorting covalent bonding. Through the whole proposal, we could further understand the condition for forming covalent bonds and its distortion effect on the crystal, electron and physical properties. Moreover, it is expected to obtain one or two kinds of novel electromagnetic compounds with significantly academic value or potential applications.

在近年来新发现的超导体和电磁相变化合物中，除了准二维的载流子库层（[La2O2]2+和[Ca2F2]2+等），还存在一类由阴离子共价键结构组成的载流子储存基元，如As-离子组成的zigzag的链，二聚体[Se2]2-离子和 Bi2-组成的平面四方形等结构。调节化合物的成份可以诱导共价键结构产生畸变，实现电荷的释放和转移，达到载流子浓度调控和“自掺杂”的目的。本项目基于前期的研究工作，以包含Tm（Tm = W, Fe, Co, Rh和Ir等）、X（X = As,Se和Te等）的二元或多元化合物为研究对象，着重设计新型阴离子共价键（X-X）的载流子储存基元，诱导其结构畸变和表征载流子浓度，探索新的超导和电磁相变等物性。通过本项目的研究，深入认识阴离子形成共价键的条件，理解共价键的畸变对晶体、电子结构和物性的影响规律，争取获得1-2种具有重要学术价值或潜在应用价值的新型电磁化合物。

项目以TmX（Tm = W, Fe, Co, Rh和Ir等;X = As,Se和Te等）的二元或多元化合物为研究对象，着重设计新型阴离子共价键（X-X）的载流子储存基元，诱导其结构畸变和表征载流子浓度，探索新的超导和电磁相变等物性。在项目执行期间内，项目组着重研究了15种该类化合物的晶体结构、电学、磁学等特性，总结了阴离子共价键和物性之间的影响规律。代表性成果为，(1)发现了新型的CuAs基超导体，阐明了As-As共价键的成键状态与超导临界温度的密切的对应关系；(2)发现了BaNaO4中 (O2)-共价键与磁矩相互作用规律，证实了O-O共价键的调控能有效地诱导出铁磁相变。通过本项目的实施，项目组揭示了阴离子共价键的成键状态对能带和电子结构有深刻的影响，与物性是密切关联的，对于丰富和发展新型的物性决定基元，设计和制备优异性能的超导和电磁功能材料具有重要作用。在本项目的资助下，共发表PRL和JACS等文章20篇，培养了硕博研究生4名，圆满完成了既定目标。