芳烃超导体的晶体结构和电子态的理论研究

In 2010, the discovery of superconductivity in K-intercalated picene and phenanthrene opened up a new research field of aromatic supercondcutor. For a new material, the crystal structure is the base to investigate its physical and chemical properties. So, the determination of superconducting phase from various crystal phases coexisted in sample and displaying the accurate electronic structure are the difficult problems in theoretical and experimental study at present. By the means of structure prediction, transition state search, X-ray diffraction peak fitting and Raman spectra simulation methods, we take K-doped picene and cronene as the typical compounds to find out and investigate the atomic structure of superconducting phase. We also adopt several exchange-correlation potentails to simulate the electronic states, and extract and induce the key feature of electronic structure for metal-doped aromatic hydrocaborn superconductors. Then we will design and predict some new aromatic superconductors by substitution of atomic group, tailoring or replacing different metal atoms. The dynamic characters of these compounds will be studied, including phonon frequency, electron-phonon coupling strength, estimation of superconducting transition temperature. Our research project is important for the understanding to the electron, spin, orbital and lattice interaction, and can provide a scientific basis for the exploration of the pairing mechanism in the metal-intercalated aromatic superconductor.

2010年，菲和苉晶体（钾掺杂）中超导电性的发现，开辟了芳烃超导研究的新领域。作为新材料，其晶体结构是一切性质的研究基础。当前，从多个结构相中确定真实的超导相，准确把握其电子结构，是实验和理论上的研究瓶颈。本课题以苉、六苯并苯等芳烃晶体为代表材料，借助结构搜索（CALYPSO软件）、过渡态寻找（NEB方法）、X-ray衍射谱模拟和Raman谱模拟，结合实验数据，甄别并确定出真实超导相的晶体结构；运用多种关联近似下的电子态模拟和理论分析，归纳出芳烃超导体电子结构的关键特征；通过取代、剪裁原子基团，替换掺杂金属等方法，设计和预测新的芳烃超导体；模拟掺杂后体系的声子谱，判断所预测结构的动力学稳定性，计算电声耦合强度，依据MacMillan公式估算其对超导的贡献。该研究有利于全面准确地理解该类材料中电荷、自旋和晶格等自由度间的相互作用，为揭示其超导配对机制提供重要的科学依据。

本项目旨在研究芳香烃类新型有机超导体的晶体结构、电子特性和磁性。在本项目执行期内，根据研究计划，完成了如下主要工作：1，从理论上确定了钾掺杂菲的稳定结构及掺杂浓度，给出其相应的电子结构特征。2，强调了分子层间的相互作用，确定了钾掺杂的对三联苯的晶体结构和基本电子结构。3，确定了phenanthrene、p-terphenyl、anthrene中的Raman位移与电荷转移的关系。4，确定了钐掺杂菲的磁性基态、反铁磁序及其轨道磁矩。5，计算了含芳烃π键的硼烯、硼碳单层的声子谱及电声耦合及超导转变温度。6，研究了钡、钾不同掺杂金属和钾钡共掺情况下对芳烃晶体电子结构的影响。此外还研究了有机金属二茂钴和锂掺杂的铁氮化物CaFeTeN中的磁性。本项目发表论文22篇，SCI一区论文6篇，二区top期刊论文6篇。 本项目核心成果是从理论上率先确定了金属掺杂芳烃晶体的稳定结构和掺杂比例，解决了该领域的一个瓶颈问题。本项目的研究为全面准确地理解芳烃超导体中电荷、自旋、轨道和晶格之间的相互作用，为进一步揭示该类材料中超导电性起源和形成机制提供了重要的理论基础。