1. Low-Dimensional Carbon Based Systems: First-principles Studies
Rui Pang, Yangfan Shao, Qian Wang, Xiji Shao, Xingqiang Shi*
Department of physics, South University of science and technology of China
Introduction
Graphene/MoS2 for Lithium storage .
Carbon based materials provide the most abundant structural varieties. This property generates a mount of complex phenomenon and gives a great deal of opportunities to realize novel functionalities. Our works mainly focus on the organic/metal interfaces, lithium storages, and novel two dimensional materials.
Magnetism on reconstructed organic/metal interfaces
Graphene/MoS2 composites exhibit excellent Li-storage capability. Band-gap opening of graphene is found in Gr/Li(n)/MoS2; the band-gap is enlarged with the increasing number of intercalated Li atoms. And, the Dirac cone feature of graphene is always preserved.
(a)
(b)
Due to strong interactions between ferromagnetic metal surfaces and fullerenes, reconstruction could happen at the interface of C60/Fe(100) and C60/Ni(111). Fig. (a) shows the fullerene creates a 4-atom-hole at Fe(100) and an antiferromagnetic coupling appears between the fullerene and the substrate. Fig. (b) shows the fullerene remove seven atoms on Ni(111) and have a remarkable enhance on the spin polarization of the molecule and a distinct reduce on the magnetic coupling and magnetocrystalline anisotropy energy (MAE) of the two outer most substrate layers.
Two reasons for the high Li-storage capability: 1) The left panel, the binding energy per Li increase with increasing number of Li atoms; 2) the right panel, for Li-atom diffusion in the graphene/MoS2 interface, the diffusion barrier is small, ~0.25eV.
Molecular Precursors-Induced Surface Reconstruction
2-D iron-carbides (Fe-C)
Unreconstructed
Reconstructed
We demonstrate that the Pt(111) surface reconstruction occurred at the earlier stages of graphene formation when there were (partial) hydrogens remain in the hydrogenated precursors of C2H4 and planar C60H30 molecule.
The reason is attributed to the fact that the energy gain, from the strengthened Pt−C partial sp3−like bonding for C with partial H (than Pt−Gr bonding), compensates for the energy cost of formation surface vacancies and makes the reconstruction feasible (especially at elevated temperatures).
We propose and demonstrate that the square-lattices observed in the experiment were monolayer iron-carbides (Fe-C) but not pure Fe, from the square-lattice shape, Fe-Fe distance, energetic and dynamic stability considerations. High spin-polarization and out-of-plane magnetization are found in this system.