Giant Axial Electrostrictive Deformation in Carbon Nanotubes

An exceptionally large axial electrostrictive deformation is demonstrated in single walled carbon nanotubes using Hartree-Fock and density functional quantum mechanics simulations. Armchair and zigzag open-ended tubes and capped tubes are studied and in all of them the external electric field induced axial strains can be greater than 10% for a field strength within $1\mathrm{V}/\AA$. The corresponding volumetric and gravimetric work capacities are predicted to be three and six orders higher than those of the best known ferroelectric, electrostrictive, magnetostrictive materials and elastomers, respectively.

Figure 1

Axial electrostrictive deformation ratio induced by external applied electric field in $(3,3)$ metallic single walled CNTs of different lengths and a $(5,0)$ semi-metallic tube.

Figure 2

Average elongation ratios of the C-C bonds having a contribution to the deformation along the direction of the external electric field for the $(3,3)/42$ tube and the corresponding planar graphite sheet.

Figure 3

The contour plots of charge density [in units of $0.0005e/(\mathrm{a}\mathrm{.}\mathrm{u}\mathrm{.}{)}^3$] for the electron structures of the $(3,3)/66$ tube predicted by the DFT technique. (a) Charge density of the HOMO with energy of $-3.28\mathrm{e}\mathrm{V}$, and (b) charge density of the LUMO with energy of $-0.61\mathrm{e}\mathrm{V}$ in the released state. (c) Charge density of the HOMO with energy of $-12.71\mathrm{e}\mathrm{V}$, and (d) charge density of the LUMO with energy of $-10.70\mathrm{e}\mathrm{V}$ under the electric field of $0.361\mathrm{V}/\AA$.