Positron Annihilation in Perfect and Defective TiO sub(2) Rutile Crystal with Single Particle Wave Function: Slater Type Orbital and Modified Jastrow Functions

Positron annihilation in TiO sub(2) rutile crystal is studied by an assumption that a positron binds with valance electrons of a titanium dioxide to form a pseudo TiO sub(2-)positron molecule before it annihilates with these electrons. The orbital modification consisting of explicit electron-positron and electron-electron correlation in each electronic orbital is used for the electrons and positron wave functions. By these wave functions, the calculation results of the positron lifetimes in unmitigated and defective TiO sub(2) crystals are about 170 ps, 266 ps and 243 ps, respectively. These results are in good agreement with experimental data of the positron lifetimes in vacancies of TiO sub(2) from 180 ps to 300 ps.