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We use the ab initio density functional theory to calculate the band structure, density of states, charge transfer, charge density difference, binding energy and vibration frequency. We can see that the conduction band through the Fermi level include SWNT/H_2/Li, SWNT/H_2/Al and SWNT/H_2/Ca, which shows a kind of metallic character. The charge distribution and contour plots of charge difference density of ion/H_2/SWNT show charge transfer between ion and H_2 molecules rather than between H_2 and H_2. Meanwhile, the interaction between Al, Ca and H_2 is weaker than that of Li. We can also prove that the ion is the primary reason to the increase of adsorption energy of hydrogen molecule in SWNT. Finally, we calculate the vibration frequency and don’t find any imaginary frequency, which proves that the(7,0) SWNT is more stable.
We use the ab initio density functional theory to calculate the band structure, density of states, charge transfer, charge density difference, binding energy and vibration frequency. We can see that the conduction band passes through the Fermi level include SWNT / H_2 / Li, SWNT / H 2 / Al and SWNT / H 2 / Ca, which shows a kind of metallic character. The charge distribution and contour plots of charge difference density of ion / H_2 / SWNT show charge transfer between ion and H_2 molecules rather than between H_2 and H_2. Meanwhile, the interaction between Al, Ca and H_2 is weaker than that of Li. We can also prove that the ion is the primary reason to the increase of adsorption energy of hydrogen molecule in SWNT. Finally, we calculate the vibration frequency and don ’ t find any imaginary frequency, which proves that the (7,0) SWNT is more stable.