SIGMA
Posted: Mon Jan 25, 2016 3:35 am
In one of the sessions about the oxygen atom, why should SIGMA be reduced when symmetry is lowered?
Dear hongbiao,
The oxygen atom is very subtle. Large smear gives you the occupations (which you can check from OUTCAR):
up: 1 1 1 1 0 0
down: 1 0.33 0.33 0.33 0 0
Small smear gives you:
up: 1 1 1 1 0 0
down: 1 1 0 0 0 0
The latter electronic occupation is lower in energy. You will find more discussions about this issue if you search more (forums , published literature, and tutorials).
Mostafa