[QE-users] calculation of non stable state

[Lorenzo Paulatto]

>> OCCUPATIONS
>> 2.
>> 0.


I said something stupid before, the occupation cannot be more than 1 per 
band, when using nspin=2.

But the root of the problem is that the code needs to know how many 
bands you have *before* reading the occupations, and for some reason 
this does not work if you do not specify the number of bands by hand.

I repeat: you *must* specify nbnd by hand when using fixed occupations. 
It is actually written in the doc:

'from_input' :

     The occupation are read from input file,
     card OCCUPATIONS. Option valid only for a
     single k-point, requires nbnd to be set
     in input. Occupations should be consistent
     with the value of tot_charge.

Anyway, what works is:

** case 1 **
nbnd=1
nspin=1
  ...
OCCUPATIONS
2


** case 2 **
nbnd=2
nspin=2
  ...
OCCUPATIONS
1 1
0 0

** case 3 **
nbnd=1
nspin=2
  ...
OCCUPATIONS
1
1


Cases 1 and 3 should give the same total energy. Of course, you can 
always specify more bands than necessary and add more zeros in each 
line, actually, extra numbers at the end of the line are ignored.




-- 
Lorenzo Paulatto - Paris