Prediction of the Pressure-Induced Phase Transition in GaAs by the Positron Affinity

The thermalized positron charge distribution is calculated as a function of pressure variation in GaAs. Calculations have been carried out via the independent particle method (IPM) coupled with the empirical pseudopotential method (EPM). Initial results show a clear asymmetrical positron charge distribution relative to the bond center. From this positron affinity we have calculated the ionicity character with respect to the pressure variation using our empirical formula. Our results show an agreement with the thermochemical phase diagram proposed by Phillips.