We report a new graphene allotrope named HOT graphene containing carbon hexagons, octagons, and tetragons. A corresponding series of nanotubes are also constructed by rolling up the HOT graphene sheet. Ab initio calculations are performed on geometric and electronic structures of the HOT graphene and the HOT graphene nanotubes. Dirac cone and high Fermi velocity are achieved in a non-hexagonal structure of HOT graphene, implying that the honeycomb structure is not an indispensable condition for Dirac fermions to exist. HOT graphene nanotubes show distinctive electronic structures depending on their topology. The (0,1) n (n ≥ 3) HOT graphene nanotubes reveal the characteristics of semimetals, while the other set of nanotubes (1,0) n shows continuously adjustable band gaps (0~ 0.51 eV) with tube size. A competition between the curvature effect and the zone-folding approximation determines the band gaps of the (1,0) n nanotubes. Novel conversion between semimetallicity and semiconductivity arises in ultra-small tubes (radius < 4 Å, i.e., n < 3).

我们报道了一种新的石墨烯同素异形体，名为HOT石墨烯，其中含有碳六边形，八边形和四边形。还可以通过卷起HOT石墨烯片来构造相应系列的纳米管。从头计算是对HOT石墨烯和HOT石墨烯纳米管的几何和电子结构进行的。在HOT石墨烯的非六边形结构中实现了狄拉克锥和高费米速度，这表明蜂窝结构并不是狄拉克费米子存在的必要条件。HOT石墨烯纳米管根据其拓扑结构显示出独特的电子结构。的（0,1）ñ（Ñ  ≥3）HOT石墨烯纳米管显示出半金属的特性，而另一组纳米管（1,0）n随管尺寸显示出连续可调的带隙（0〜0.51 eV）。曲率效应和区域折叠近似之间的竞争决定了（1,0）n个纳米管的带隙。在超小管中（半径<4Å，即n  <3），出现了半金属性和半导电性之间的新型转换。