Dear all,
my question concerns in particular the "numbering" of the wavefunctions
that one gets after using denchar to produce *.WFSX files after a
completed siesta run. I have to get the correct wavefunctions that
correspond to the highest occupied molecular orbital (HOMO) and the
lowest occupied molecular orbital (LUMO), that is- the wavefunctions
with the index of the eigenvalue directly below and directly above the
fermi energy, respectively. The problem I face is the following: Let's
say my system would have 20 eigenvalues, and the index corresponding to
HOMO and LUMO are 5,6 (spin up) and 15,16 (spin down). I would expect
denchar to produce spin up wavefunctions for the lower half (1-10) of
the available indices, and spin down wavefunctions for the upper half
(11-20), since apparently that is the way siesta stores the eigenvalues
in the *.EIG file. However, denchar produces spin up AND spin down
wavefunctions for EACH index, i.e. if i were to write out all
wavefunctions with indices 1-20 I would get 40 wavefunction files, where
I should only have 20- that is 10 for spin up and 10 for spin down.
So now my question is: what are these other 20 wavefunctions? In
particular, what do the *.DOWN.cube files mean that denchar produces for
the LOWER half of the indices (which should only correspond to spin up
eigenvalues) and what do the *.UP.cube files mean for the UPPER half of
the indices (which should only correspond to spin up eigenvalues)
I hypothesized that there might be "dummy" indices that denchar writes
out and I made a test with a H2O molecule that I assigned a NetChage -1
(so that its eigenvalues are different, for different spins) to, to find
out which indices may be "dummy". The H2O gave me 23 eigenvalues per
spin / 46 in total. Then I produced all wavefunctions with indices from
0 to 100, just to see what happens if I even exceed the number of total
eigenvalues. Denchar still produces wavefunction files that are often
only filled with zeros, but not always... Also, no combination of
"dummy" I could think of made sense with the output denchar produced. I
compared all 100 wavefunctions pairwise, whether the wavefunction data
is identical or not, but I could not identify any of the following
"dummy scheme" that I could understand:
lower half(spin up) = upper half(spin up) and lower half(spin down) =
upper half(spin down)
lower half(spin up) = upper half(spin down) and lower half(spin down) =
upper half(spin up).
In particular I do not understand why denchar still produces
wavefunction files with indices that exceed the number of eigenvalues
(and if so, why the wavefunction data is not only zero!).
If anyone could tell me what denchar is doing/ how it is numbering
wavefunctions and which ones are dummy/ which ones not, I would be
extremely grateful since I cannot find any documentation about this and
also nothing on the mail archive.
Sorry if this text was to long, here again in short:
Denchar produces spin polarized wavefunction output I do not expect /
understand. Denchar can produce more wavefunction files than indices of
wavefunctions exist in a given system and I can't identify a dummy
indexing scheme. Denchar does not order spin up / spin down wavefunction
output in terms of the index in a way I can understand.
Regards,
B.
