Carbon three-dimensional architecture formed by intersectional collision of graphene patches

Abstract

Graphite is the most stable form of carbon under room temperature and atmospheric pressure, and consists of two-dimensional honeycomb lattices with intralayer $s{p}^{2}$ bonding and rather weak van der Waals like interlayer interaction. When we supply gaseous small carbonic molecules such as methane to a patch of graphene, the patch will grow into graphite. Now, let us imagine a slightly different situation. Is a layered structure of graphite always formed, when we supply not methane molecules but another graphene patch? The answer from our computer simulations is ``No.'' Some graphene patches collide in parallel, but others at right angles, which result in a formation of junction structures (graphitic Y junctions). These junction structures are different from those of common sense for graphitic materials. Performing density functional calculations, we found that the reaction barrier height required for the formation of graphitic Y junctions are almost zero, and the binding energies per bond for each structure are $\ensuremath{\sim}1\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. Furthermore, tight-binding molecular dynamics simulations showed high thermal stability and high formation probabilities for these junction structures. As applications of graphitic Y junctions, we will present two interesting structures, where we focus on the magnetic properties of junction structures and nanotube T-junction structures which are different from conventional models. We expect that graphitic Y junctions might be hidden in graphitic soot and not characterized yet in experiment. 3D architectures constructed from those unit structures are expected to have various applications with lightweight, ferromagnet, high molecular storage and high thermal conductor.