芳香烃超导材料制备中涉及的化学反应的理论研究

Ever since the discovery of the high superconducting transition temperature for potassium doped picene in 2010, the metal-intercalated aromatic superconducting materials have been among one of the most important subjects in physical sciences. The sythesis of the materials still confronts lot of issues, such as the poor crystallization, low content of superconducting shielding field and the preference towards multiphases, which make the experimental and theoretical studies very difficult. Moreover, few work about chemical reaction involved has been reported. Thus, the chemical reactions involved in the metal intercalating aromatic materials process play a key role in revealing the microscopic process. In this project, based on chemical reaction theories, the first-principles calculations will be carried out to study the heterogeneous chemical reactions for potassium, barium, lanthanum and samarium intercalated phenanthrene crystal systems. Models of chemical reactions such as atomic metals with single phenanthrene molecule, atomic potassium on the phenanthrene surface, phenanthrene molecule on the barium, lanthanum and samarium surfaces, will be used to reveal the mechanisms of 1) forming metal-phenanthrene complex, 2) activating the C-H bonds by metals and the formation of metal hydrides, and 3) breaking and closing the C-C bonds in phenanthrene by metals. This project will clarify the stability of metal-intercalated aromatic materials and the chemical reaction mechanism for metal hydride formation, and provide scientific basis for further experimental and theoretical studies of the metal-intercalated aromatic materials, as well as an important support for exploring new superconducting materials.

具有高超导转变温度的钾掺杂苉材料于2010被实验发现，使得金属掺杂芳烃超导材料成为物理、材料、化学等领域的重要研究内容。这种材料合成制备中存在结晶性差、超导成分低、易形成多相等问题，使得进一步实验和理论研究有很多困难。目前，也少见相关化学反应的报道；而从化学反应角度清楚理解金属掺杂芳烃材料的过程对澄清上述问题有关键的作用。本项目将基于反应理论，使用第一性原理计算方法，对钾、钡、镧和钐掺杂菲分子晶体所涉化学反应进行研究，包括：金属原子-菲单分子、钾与菲晶体表面、菲分子与钡、镧和钐金属表面等反应。我们的研究将得到1)金属-菲分子化合机理；2)金属对菲C-H活化作用及金属氢化物产生机理;3)金属对菲C-C活化作用及开环-闭环机理影响。本项目将澄清金属掺杂芳烃的稳定性和金属氢化物产生的化学反应机理，从而为新型超导材料的实验和理论研究提供保障和支持。

金属插层芳烃材料因其潜在的室温超导电性能成为物理、材料、化学等领域的重要研究内容。本项目从气相、体相和表面等多个角度对钾等碱金属与菲、三联苯等芳烃之间的电荷转移和氢抽取等化学反应进行了系统研究。对电荷转移与稳定结构、磁性、电学和光学性质进行了研究：1）对芳烃分子在不同荷电量下的拉曼光谱进行了计算，通过与实验数据对比确定了材料体系中金属芳烃的化学计量比；2）研究了钾钡共掺菲晶体在分子边缘分布而非均匀分布的Bader电荷、铁磁和反铁磁的稳定性，确定了菲分子不均匀的电荷分布对磁矩的贡献；3）结合Marcus理论研究了杂芳烃-噻吩类化合物的导电和光学性能，取代基电子效应的差异导致了不同的电荷转移效果，进而改变了体系的载流子迁移速率和发光效率。对气相、体相和金属表面的氢抽取反应进行了计算研究，结果表明：1）金属-芳烃化学计量低于2:1的条件下，钾易于菲、三联苯生成稳定的络合物；2）金属-芳烃化学计量比等于或高于3:1，能够发生氢抽取反应生成HK和金属络合物自由基产物；3）相对于体相和分子表面的氢抽取反应，金属表面的氢抽取反应更容易发生。上述研究结果为电荷对材料光学、电学和磁学等性能的调控提供了理论依据，为通过固相反应制备高纯度金属插层芳烃材料提供了支持。