The Hartree-Fock calculations from figure were also repeated to ensure that the new interaction reduces the CFSE present in these calculations. The results are illustrated in Figure . The new interaction is clearly also successful in HF calculations, reducing the CFSE by a factor of about 3.

**Figure:** The energy per atom of diamond-structure silicon as a
function of simulation cell size, from HF calculations using the
Ewald electron-electron interaction and the new interaction.

Tue Nov 19 17:11:34 GMT 1996