The tetrahedron method with Blöchl corrections (ISMEAR=-5) gives a good account of the electronic density of states (DOS). The only drawback is that the method is not variational with respect to the partial occupancies. Therefore the calculated forces and the stress tensor can be wrong by up to 5 to 10% for metals. Only for semiconductors and insulators, the forces are correct because the partial occupancies do not vary and are either zero or one.
ISMEAR
| property | Relaxation | Single point |
|---|---|---|
| Metal | 1 or 2 | -5 |
| Semiconductor | -5 | -5 |
| Insulator | -5 | -5 |
| Unknown | 0 | -5 |