| This thesis reports the improvement and extension of the self-consistent tight-binding(SCTB) method and its application to study of the oxide-water interface. The improvements we describe in this thesis are: (1) electronic dipole-dipole interactions, which proved to be important in liquid water; (2) constant-pressure capability, which is essential in simulating phase diagrams; (3) k-sum calculation of electronic structure, which enhanced the accuracy of small super-cell calculations; (4) character table calculation, which makes the identification of band structure universal for any crystal and (5) external electric fields at interfaces, which makes study of field-induced phase transitions possible. Two new suites of codes have been developed for the fitting and simulation aspects of the SCTB method. We have applied this method to develop a SCTB model for dissociable liquid water and reproduced the radial distribution function, ion conductivity, phase diagram, and properties of hydronium in liquid water. The probability distribution of hydronium is compared with first-principles results. We simulated rutile titanium dioxide (110) surface in contact with liquid water. By the integration of the mean force, we found the surface free energy of the titanium dioxide-water interface. We applied the method to ruthenium dioxide, and got good agreement with experimental results on surface energies, work functions and bond lengths at surface. We studied water-RuO2 interfaces and are finding the energy as a function of external electric field for comparison with recent experiments. |
