Selection Of Calculation Model For Titanium Dioxide

This thesis use theoretical calculation to study of rutile titanium dioxide (110) surfaces inthe selection of best interception model in theoretical calculations. The main contents of thisthesis are:First, use the periodic ab initio to study on the methanol molecular adsorption anddissociation on the rutile TiO2(110) surface, so as to identify the best model for titaniumdioxide that you can choose in experiments or calculations. First, give four kinds of treatmentto the obtained model, saturated froze, unsaturated froze, and saturated relaxed andunsaturated relaxed, then through the analysis on the adsorption energy, dissociation energyand the energy barrier of transition state that obtained by the structure optimization ofmethanol molecular in different model and different layers on the rutile TiO2(110) surface,thereby get the best layer number of rutile TiO2model. Study results showed that the modelwas modified more, less dependent on the layers of model, so we get the saturated froze sixlayers of rutile TiO2(110) surface is the best for calculations.Second, calculation of DFT+U is implemented in the saturated froze part of the sixlayers model, in order to study the effect of different U-values of adsorption and dissociationof methanol on the TiO2surface. We found that, although there have been investigated, theincrease of the U value will enable the gap widened. But our data analysis shows, not allproperties are improved. So we think that using U=4.1eV or4.2eV is the best to theresearches that care the energy gap calculation more, but to the study that aim the change ofkinds of energies and the energy barriers in the process of adsorption and dissociation ofmethanol adsorbed on the surface of titanium dioxide as the main research contents, U=3eV isthe most favorable.