The electronic and positronic structure of defects in materials

We have employed a first-principles supercell methodology based on the charge selfconsistent KKR band theory framework in order to investigate the electronic and positronic structure of defected systems. Judicious use of the KKR-CPA disordered alloy theory in conjunction with the supercell calculations allows us to gain insight into effects of vacancy concentration, of electronic relaxation, and of electron-positron correlation on the positron state. We illustrate our approach by considering examples of a monovacancy in Al and Si, a single P impurity in Si, and the As-vacancy complex in Si.