Electron and positron response to atomic defects in solids: A theoretical study of the monovacancy and divacancy in aluminum

A formalism for self-consistently calculating the response of electrons and positrons to atomic defects in solids is presented. The formalism can be used with either the Green's-function or supercell method for calculating defect characteristics, and is of general applicability. With the use of this formalism and the self-consistent pseudopotential scheme within a supercell, the electronic structure and positron states and annihilation characteristics associated with the monovacancy and divacancy in aluminum have been studied. The sensitivity of the calculated monovacancy electronic structure and formation energy to the type of ionic pseudopotential used is also examined. Finally, the possibilities for using positron-annihilation spectroscopy to study the electronic structure of vacancylike defects are considered.