Positron Annihilation in Perfect and Defective TiO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Rutile Crystal with Single Particle Wave Function: Slater Type Orbital and Modified Jastrow Functions

Trinh Hoa Lang,Kieu Tien Dung,Le Hoang Chien,Chau Van Tao

doi:10.4236/wjnst.2014.41006

Abstract

Positron annihilation in TiO2 rutile crystal is studied by an assumption that a positron binds with valance electrons of a titanium dioxide to form a pseudo TiO2-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 TiO2 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 TiO2 from 180 ps to 300 ps.

Highlights

The structure of material is studied by positron lifetime spectrum, which has many lifetime components depending on a local structure where a positron annihilates with electrons
The enhancement factor and positron lifetime in a perfect TiO2 rutile crystal are determined from these parameters
The enhancement factor and positron lifetime in TiO2 rutile crystal of an oxygen defect, created by removing function parameters of electron and positron in the TiO2 rutile crystal of a titanium defect is still valid, and the one oxygen atom from a unit cell of TiO2 perfect rutile distribution of electron-positron pair correlation is obcrystal, are calculated from these parameters, which tained from Monte Carlo simulation as shown in Figure is assumed that they is still valid for the electron and 4(a)

Summary

Introduction

The structure of material is studied by positron lifetime spectrum, which has many lifetime components depending on a local structure where a positron annihilates with electrons. The problem is how to determine accurately lifetime components of a positron in experiments It encourages studying deeply the positron annihilation in element-specific structure of materials such as a single atom, a molecule or a unit cell. By choosing a trial single wave function, the VQMC method is used to find the ground state of positron-valence electron of a unit element. In this scenario, the optimized electron and positron distributions in real space of unit structure of material are determined by the minimal energy.

Theory

Results and Discussion

Conclusions