Rigid-pseudoion model

The foundation of the "rigid-pseudoion" model is the "rigid-ion" description of the lattice dynamics, which was introduced by Nordheim. In this approximation, the ion-core potential of an atom moves rigidly when the atom is displaced from equilibrium. Thus, the potential seen by an electron due to a lattic of such atoms is justr, 24,27,28... 

However, the agreement which we have obtained through our potential is good and can be taken as a demonstration of the validity of the "rigid-pseudoion" model for calculating EP and HP matrix elements. 

Based on the success of both our calculations and those of Ref. 12 we conclude that the "rigid-pseudoion" model provides a good description of the EP and HP intervalley scattering matrix elements in Ge and Si. One of the questions to be resolved is the difference in the extrapolation of the form factor between our work and that of Ref. 13. This may be due to the empirical nature of the pseudopotential that has been used and suggests that a more self-consistent approach should be tried. Also the extension of the present work to zincblend-type materials is an area of considerable interest. 

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