Structures and Solid-Liquid Phase Transition of High-Density Hydrogen Confined in Single-Walled Carbon Nanotubes

Abstract:

Hydrogen with ultrahigh density confined in single-walled carbon nanotubes (SWCNTs) was investigated using density functional theory (DFT) and first principles molecular dynamics simulations (MDSs). Hydrogen atoms injected in to the cages of the SWCNTs via atomic collisions gradually form solid H2 molecular lattice with a characteristic of spiral multi-strands structure. The concentration of H2 confined in the SWCNTs can be as high as ~ 1.77×1023H2 /cm3, and the pressure between the H2 lattice and the wall of the SWCNT can be as high as ~ 77 GPa. When the system was heated to temperature higher than 700K, a solid-liquid phase transition was observed. When temperature rose to 1000K, a few H2 molecules dissociated forming a mixed liquid of H atoms, H2 molecules, and hydrogen trimers. Electron states near the Fermi level were appeared, which were attributed to the H atoms and the trimers. The electronic properties of the quasi-one-dimensional hydrogen confined in the SWNTs were thus substantially changed.

• Periodical: Advanced Materials Research (Volumes 79-82)
• Pages: 67-70
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.79-82.67
• Online since: August 2009
• Authors: Yue Yuan Xia, Ming Wen Zhao, Xiang Dong Liu, Yan Ju Ji
• Keywords: First Principles Molecular Dynamics Simulation, High Density Hydrogen, Single-Walled Carbon Nanotube (SWCNT), Solid-Liquid Phase Transition

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[10] [20] [30] [40] DOS (number of states/eV) E-EF (eV) T= 1000K (a) -6 -4 -2 0 2 4.

[2] [4] [6] [8] [10] [12] [14] PDOS (number of states/eV) E-EF (eV) T=1000K (b) -6-4-(2024).

[2] [4] [6] [8] [10] [12] [14] PDOS (number of states/eV) E-EF (eV) T= 1000K (c) t =970fs t =1145fs t =700fs t =800fs Fig. 4 (Left column) the snapshots obtained from the simulation of the reactions of two H2 molecules in the hydrogen system confined in the (5, 5)SWNT at annealing temperature of 1000K for different time t ( t = 700fs, 800fs, 970fs, and 1145 fs, respectively), showing the process of dissociation of a H2 to form a H3 trimer and a H atom, (right column) (a) the DOS of the hydrogen system at anneal time of 1150 fs; (b) the PDOS projected on the atomic orbitals of the trimer, and (c) the PDOS projected on the atomic orbitals of a H atom.