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由于独特的成键特性,在不同温度和压强下,碳具有丰富的结构特性。除了实验上已发现各种同素异形体,理论计算也预言了丰富的新结构。在本文中,我们对第一性原理计算预言的三维碳同素异形体做了综述,我们特别关注了泡沫状的碳结构。碳泡沫主要由石墨片段以各种碳键连接而成,具有多孔结构及较大的表面积。另外,针对由低维碳结构,如碳富勒烯、纳米芽、纳米管及石墨烯带等组成的三维碳超结构以及其他三维碳晶体我们也做了概述。这些新型碳结构有的由混杂的sp-sp2碳或者纯sp2碳组成(H-6,bct-4,C-20,K4等),有的质量密度比金刚石还大(C8,hP3,tl12,tp12等),有的可以由石墨在室温高压下转化而成(M碳,bct-4碳,W碳,Z碳等)。在这些预言的碳同素异形体中,有些在将来可能在实验室合成。
Due to its unique bonding properties, carbon has a wide range of structural properties at different temperatures and pressures. In addition to the experimental discovery of various allotropes, theoretical calculations have also predicted rich new structures. In this paper, we review the three-dimensional carbon allotropes from which first-principles calculations are predictive, and we are particularly concerned with foamy carbon structures. Carbon foam is mainly composed of graphite fragments connected by a variety of carbon bonds, with a porous structure and a larger surface area. In addition, we also summarize the three-dimensional carbon superstructures composed of low-dimensional carbon structures, such as carbon fullerenes, nano-sprouts, nanotubes and graphene ribbons and other three-dimensional carbon crystals. Some of these new carbon structures consist of mixed sp-sp2 carbons or pure sp2 carbons (H-6, bct-4, C-20, K4 etc.) and some have higher mass densities than diamonds (C8, tp12, etc.), and some can be converted from graphite under high pressure at room temperature (M carbon, bct-4 carbon, W carbon, Z carbon, etc.). Some of these predicted carbon allotropes may be synthesized in the lab in the future.