Relating Fundamental Chemistry and Smart Materials with DFT Calculations

摘要

We present first-principles investigations of the properties of piezoelectric oxides and metal surfaces. Our oxide work elucidates important fundamental relationships between local atomic structure and macroscopic properties of piezoelectrics. We develop a new semi-empirical model to study large supercells of disordered complex oxides. We also present our computational materials design studies of proposed new perovskites. In particular we demonstrate for the first time the off-centering behavior of silver ions, which may lead to environmentally friendly silver-based piezoelectrics. Examining the chemical properties of metal surfaces, we present our studies in vacancy formation, the effects of strain on the adsorptive properties of metal surfaces and self assembled monolayers. We find that vacancy formation leads to electronic spillout and a strengthening of the bonds between the neighboring atoms accompanied by an inward relaxation. Our calculations show that the effect of strain on the chemisorption is sensitive to changes in coverage, metal identity and surface plane. In our studies on self assembled monolayers, we examine the complex adsorption process and the potential energy surfaces for adsorption of thiols on noble metal surfaces. We also show that formation of ordered thiol structures is favorable on Al(111) surface, indicating a possible use of self-assembled monolayers as a anti-corrosion protective coating.