APPLICATION OF COMPUTATIONAL CERAMIC ENGINEERING TO PHOTOCATALYTIC TiO2,DEFECT STRUCTURES IN TiO2,AND MULTIDOMAIN FERROELECTRICS

摘要

Computational tools on all time and length scales are playing an increasingly important part in ceramics development and manufacturing.As a survey of recent advances in the micro-and mesoscales this work explores bandgap and defect engineering of TiO2 and domain average engineering of ferroelectrics.Specifically,anion doping in TiO2 with nitrogen,phosphorous,carbon and sulfur is emphasized in this work and a discussion of the electronic structure and localization for each of these systems is presented.It is found sulfur,phosphorous and low-concentration carbon and nitrogen are fair to poor photocatalytic dopants and high-concentration carbon and nitrogen are better photocatalysts.The effect of oxygen vacancy defects in TiO2 and the free energetic barrier of these defects are discussed.A method to calculate the free energy of formation of oxygen vacancies using DFT local orbital techniques and initial results thereof are presented.The mesoscopic regime of multidomain configurations in ferroelectrics is investigated.A brief synopsis of a computationally efficient real space model for ferroelectrics is given and illustrated using domain average engineering of perovskite structures guided by multidomain group theory.