Evaluation of point-core approximation effect on the positron energy levels in diamond structure solids

Abstract

Positron work function, positron affinity, positron energy band, deformation potential and some other important positron-related parameters are studied in the elemental semiconductors which have the diamond structure, using the first-principle norm-conserving pseudopotential method. While both the local density approximation (LDA) and the generalized gradient approximation (GGA) are employed in the positron structure theoretical research, to deal with the positron-electron exchange-correlation (EC) energy, only the GGA framework is adopted in electron total energy calculation. The nonlinear core correction is included in the positron-electron EC potential and the core electrons are considered within the frozen-core model. Point-core approximation is used to model the positron-ion interact potential. The calculation results agree well with the reference data. However, the positron band effective mass which has a dominate part of the total effective mass is systematic lower than the result which is obtained from other approaches. Because of the sensibility of the positron diffusion constant to the total effective mass, it is found that the point-core approximation could not provide an accurate forecast for the diffusion parameter.