[Wien] TOT ENE

[Stefaan Cottenier]

> The Total ENE difference between the ideal crystal and the crystal with
> vacancy is not physical (over 100 Ry).  Obviously there seems to be a
> problem. (Within the crystal with vacancy calculation the relaxation
> energy is about 1.3 eV for Silicon vacancy, i think this is decent)

This is correct: you have one atom less, hence you lose roughly the total
energy of 1 free atom (e.g. about 580 Ry for Si).

You probably want to know whether the situation with the vacancy is more
favourable than the ideal crystal? One way to estimate it (which might not
be entirely correct either, can other people comment?) is this one:
calculate the cohesive energy of the cell with and without vacancy (see FAQ
how to calculate cohesive energies), and compare those.

Stefaan