This example illustrates the use of the option occupations='from_input'.

1) make an LDA self-consistent calculation for an isolated Al atom by
   specifying the occupancy of each band in the input file. There are 6 
   bands (nbnd=6) whose occupancies are:
   2.0 0.3333333333333 0.333333333333 0.3333333333333 0.0 0.0
   (input=al.in, ouput=al.out)

2) make a sigma-GGA spin-polarized (nspin=2) self-consistent calculation
   for an isolated O atom by specifying the occupancies of each band in
   each spin channel (for each k-point: only gamma in this example):
   1.0 1.0 1.0 1.0 0.0 0.0 
   1.0 0.33333333333 0.33333333333 0.33333333333 0.0 0.0 
   (input=O.in, output=O.out)

3) the sama as in point 2), but with the gamma version of the code.
   (input=O_gamma.in, output=O_gamma.out)

