[QE-users] General problems in calculation and interpretation of PDOS

[Parisa alipour kamran]

Dear Users,

I study the strain effect on the band structure of Barium Titanate (BaTiO3)
using QE in my master thesis. I used projwfc.x in order to make pdos.
Regarding our output files I have some questions, although these questions
may become elementary for you and they have been briefly described in QE
manual but I would prefer to get deeper insight, rather than using the code
as a black box.

1-    PDOS refers to partial density of states or projected density of
states or they both are equivalent.
2-    How can I get more insight about spherical harmonics? Would you give
a reference to read more about?
3-    In the beginning of the file “pdos.out” we see “atomic states used
for projection”. In case of BaTiO3 the number of states is 30. What does
this 30 mean? Number of valence electron or …. . Does this number depend to
the exploited psudopotential?
4-    In the manual of QE, (
https://www.quantum-espresso.org/Doc/INPUT_PROJWFC.html), ln the section
“order of orbital”, l and m are not clearly described, at least for me, it
is not clear that what these numbers mean.
for l=1:
    1 pz     (m=0)
2    px     (real combination of m=+/-1 with cosine)
       3 py     (real combination of m=+/-1 with sine)
5-    as a result of pdos for barium we see 4 files namely:

*.pdos_atm#1(Ba)_wfc#1(s)
*.pdos_atm#1(Ba)_wfc#2(s)
*.pdos_atm#1(Ba)_wfc#3(p)
*.pdos_atm#1(Ba)_wfc#4(p)

While 8 atomic states (for barium) have been taken into account for
projection and now we just see 4 files. How do we interpret these
differences? Would you please kindly comment on these question?



Kind Regards,
  Parisa
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