Theoretical study on the long-range electron correlation and structure in soft-condensed matter

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We have developed a semiempirical theory to investigate the effect of long-range electron correlation on the structure and dynamics of graphite and graphitic nano-structured materials. In recent years, many calculations based on the density functional theory have been performed for these materials, but these calculations are unable to predict quantitatively even the interlayer binding energy of graphite. The reason for this deficiency may be attributed to the fact that in such calculations the long-range van der Waals interaction is not taken into account at all and the electron correlations at short-and intermediate-range is not properly treated. In the present study we have revisited the semiempirical theory developed earlier and confirmed the validity of the revised theory by applying it to the calculations of the binding energy of graphite. We have also extended this theory to calculate deformation energy of single-wall carbon nanotubes and successfully predicted their radial defor … More mation under hydrostatic pressure. The radial deformations predicted by this theory are consistent with experiments, thereby confirming the usefulness of the present approach. Furthermore, we have used this theory to elucidate electronic structure modification by radial deformation in carbon nanotubes under hydrostatic pressure. These results provide a useful starting point for revealing the relation between the deformation characteristics and electronic properties, which could be useful in technological applications.As a related study, we have investigated the lithium ion adsorption on the defective carbon nanotubes using the first-principles molecular dynamics simulations and found the necessary condition to utilize carbon nanotubes as the electrode of rechargeable lithium ion battery. Systematic calculations have also been performed for the electronic structure change due to various defects and impurities in CdS and investigated the possibility of p-doping, which is quite important in practical applications. Less