ELECTRONIC-STRUCTURE, CONDUCTIVITY, AND SUPERCONDUCTIVITY OF ALKALI-METAL DOPED C-60
ELECTRONIC-STRUCTURE, CONDUCTIVITY, AND SUPERCONDUCTIVITY OF ALKALI-METAL DOPED C-60
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DOI：
10.1021/ar00015a005
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发表时间：
1992-03-01
影响因子：
18.3
通讯作者：
HADDON, RC
中科院分区：
文献类型：
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作者：
HADDON, RC
本报告总结了美国电话电报公司贝尔实验室在过去几年中对富勒烯进行的工作。在Kroto、Heath、O’brien、Curl和smalley发现富勒烯后不久，我首先讨论了这些分子的电子结构，这些结构是根据一般理论推断出来的。在Kratschmer， Lamb, Fosti-ropoulos，在本报告的其余部分，我将讨论基于这些材料的导电和超导固体和薄膜的制备和表征方面的进展，以及目前在这一领域所取得的认识状态。富勒烯最引人注目的特征是其球形几何形状，这直接决定了其奇异的电子结构。由于这些分子完全由三价碳原子组成，因此表面的存在是隐含的，并且考虑到碳的这种价态最好容纳在六元环（6-MRs）中，因此有向苯类结构发展的趋势。如果富勒烯仅由共轭6-MRs组成，如苯和石墨，它们将是交替碳氢化合物（AHs）。这种分类所赋予的更重要的性质之一是占据和未占据分子轨道之间的对称性，也就是说，成键和反键HMO能级在能量为零的地方是对称的。因此可以预期，苯类碳氢化合物和石墨同样容易接受和提供电子。通过适当调整参比电位，这些化合物确实表现出镜像还原电位和氧化电位。此外，聚乙炔和石墨（无限的一维和二维AHs）在固体状态下经历n型和p型掺杂。苯环的一致性产生了表面，最终产生了石墨，但由于薄片外围的碳价不理想，不可避免地会产生悬垂键。富勒烯的天才之处在于创造了一种环境，在这种环境中，其他结构可能性的形成与具有悬空键的纯苯类碎片的产生是竞争的。1,5为了完全去除悬空键，必须消除表面的边缘，这需要
This Accountsummarizes work carried out at AT&T Bell Laboratories on the fullerenes during the past few years. I begin with a discussion of the electronic structure of these molecules which was inferred from general theories soon after the fullerenes were identified by Kroto, Heath, O’Brien, Curl, andSmalley. 1 The high electron affinity2, 3 and the existence of radiating x-orbitals4 when combined with simple ideas for the design of molecular metals and superconductors led us to pursue conductivity and superconductivity in the alkali metal doped fullerenes immediatelyafter the synthesis of C60 and C70 by Kratschmer, Lamb, Fosti-ropoulos, and Huffman. 5 In the remainder of the Ac-count I discuss the progress in the preparation and characterization of conducting and superconducting solids and films based on these materials and the cur-rent state of understanding which has been attained in this field.The spheroidal geometry of the fullerenes is their most arresting feature, and it directly determines their singular electronic structure. As these molecules are solely composed of trivalent carbon atoms, the presence of a surface is implied, andgiven thefact that this valence state of carbon is best accommodated in sixmembered rings (6-MRs), there is a tendency toward benzenoid structures. If the fullerenes were composed solely of conjugated 6-MRs, such as occurs in benzene and graphite, they would be alternant hydrocarbons (AHs). 6 Among the more important properties this classification confers is symmetry between the occupied and unoccupied molecular orbitals, that is, the bonding and antibonding HMO energy levels are symmetrically disposed about the energy zero. 6 Thus it is to be ex-pected that benzenoid hydrocarbons and graphite will accept and donate electrons with equal ease. With appropriate adjustment of the reference potential, these compounds do exhibit mirror-image reduction and ox-idation potentials. 7 Furthermore, polyacetylene and graphite (the infinite one-and two-dimensional AHs), undergo both n-and p-type dopingin the solid state. 8 The homologation of benzene rings produces a sur-face, and ultimately graphite, but with the inevitable dangling bonds due to the unsatisfied carbon valencies at the periphery of the sheet. The genius in the pro-duction of the fullerenes was the creation of an environment in which the formation of other structural possibilities was competitive with the generation of a purely benzenoid fragment with dangling bonds. 1, 5 In order to remove the dangling bonds entirely, the edges of the surface must be eliminated, and this requires the