Quantum Mechanical Studies of Electron Transport Processes Including Superconductivity

Doktorsavhandling, 2001

Processes of electron transfer, charge and spin localization, and electron pair transfer have been studied on the basis of the Marcus model and with the help of accurate quantum chemical calculations. A vibrational model, based on the corrections to the Born-Oppenheimer approximation, which applies in the case of a vanishing barrier in the Marcus model, has been proposed. Molecular polaron formation energy in anthracene crystals is estimated, using ab initio methods. The results are in agreement with the measured energy structure of polaron states. A quantum-mechanical model for the description of charge localization in crystals is proposed. 'Sharp' metal-insulator transition at a certain ratio between the site reorganization energy l and intersite coupling .lambda. follows from the model, as demonstrated for anthracene. First-principle calculations of electric currents in the ground state of CuO2 planes are performed on the basis of a model for superconductivity in high-Tc cuprates. A computer graphics program has been written for visualization of the results. Potential energy surfaces, corresponding to a 'breathing' vibrational mode of the CuO2 plane in undoped La2CuO4 have been calculated. A computer program for the calculation of the Madelung potential in molecular or inorganic crystals of any space group has been written. User-friendly interface and completely automatic treatment of symmetry contributes to making it a useful tool among modern quantum chemical software.