The binding energy of H to a (10,0) carbon nanotube is calculated at 24, 50, and 100% coverage.Several different bonding configurations are considered for the 50% coverage case. Using the ONIOM approach, the average C-H bond energy for the most stable 50°'/0 coverage and for the 100% coverage are 57.3 and 38.6 kcal/mol, respectively. Considering the size of the bond energy of Hz, these values suggest that it will be difficult to achieve 100% atomic H coverage on a (10,0) nanotube.

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Molecule−surface interaction energies are computed at the B3LYP level of theory. The C(111) and Si(111) surfaces, with H, F, or CN covalently bonded to the surface, are studied. The incoming molecule simulates the tip of a probe that should be able to differentiate between the atoms or molecules on the surface. A Sc-tipped probe molecule yields a larger difference for the probe−surface H versus probe−surface F interaction energies than our previously studied, electron-rich pyridine (C5H5N) and (CH3)3PO probes. However, it is not always possible to differentiate between the surface H and F atoms because the Sc probe interacts too strongly with the neighboring surface atoms. The difference in the probe−H and probe−F interaction energies is smaller for Si(111) than C(111), making it more difficult to differentiate between these two atoms on Si(111). The larger lattice constant for Si(111) significantly reduces the surface atom−surface atom interaction energy as well as the probe−neighbor interaction energies. This means that the H/CN system, which is not practical for C(111) due to the CN−CN repulsion, is possible for Si(111). The difference in the probe−H and probe−CN interaction energies is very large for the H/CN data storage system, making this the best system studied to date.

The self-consistent-field plus configuration-interaction method has been used to compute potential energy curves and certain one-electron properties for the X l~+. C l~-. A In, and E I~+ states of SiD. This study employed a basis consisting of 51 Slater-type orbitals which is an expanded version of the one reported by McLean and Yoshimine. The computed ground-state dissociation energy (De) of 8.1 eV is in excellent agreement with the experimental value of 8.26±0.13 eV. The theoretical ground-state electric dipole moment function is in good agreement with the experimental curve constructed from the microwave data for the v = ()"'3 vibrational levels. Einstein A coefficients for vibration-rotation transitions computed from existing theoretical and experimental data are in good agreement. The E I ~ + state is shown to dissociate adiabatically to ground-state atoms over a potential barrier with a maximum near 5 bohr. Calculated transition probabilities and radiative lifetimes for the A I n-X I ~+ and E I ~ + -X 1 ~ + band systems agree well with recent laboratory experiments. Absorption cross sections as a function of wavelength have been computed and used to determine the opacity of SiD boundary layers that will form on the surface of probe vehicles entering the Jovian atmosphere at high speeds. These calculations demonstrate that the brilliant shock layer emission will be significantly absorbed by the SiD A In-x I~+ and SiD E I ~ + -X 1 ~ + band systems in the boundary layer in the spectral region between 170 and 230 nm.