Hi,
Yes, for sure you can forget the "Blm" and most important are the "Alm".
There are 2 problems:
You may have some "Clm" (local orbitals), which could be dominating !
While this is probably less important for real "semicore states" as you
may not use them for PES, it might be important for something like C or
O s states or Ti-4s,4p valence states. The problems can be avoided when
modifying case.in1 and removing the local orbitals for the atoms with
low valence states like O-2s, ....; and for the atoms with semicore
states, put the 4s as APW and the 3s as LO (2nd line in case.in1).
The more critical problem is that the ALMs give you only the amplitude
and phase INSIDE the atomic sphere.
Checkout case.outputst, and you will see how much l-like charge of a
particular atom is within the atomic sphere.
For instance for Ti (RMT=2.25)
3D* -0.355365 -0.246227 2.00 0.00 0.8136 F
4S -0.342909 -0.306636 1.00 1.00 0.1495 F
++++++
it means that 81 % of the 3d charge is inside the sphere, but only 15%
of 4s charge.
This has the consequence that a pure 3d state might have a
"alm=sqrt(0.8)", but a PURE 4s state has only alm=sqrt(0.15).
This is the reason, why we introduced the "renormalized partial DOS",
where the interstital DOS is removed and the 3d PDOS will be slightly,
the 4s PDOS strongly enhanced. You should probably use a similar concept
and use the renormalization factors given in the output of a rendos
calculation.
Regards
Peter Blaha
Am 16.02.2024 um 23:28 schrieb pluto:
Dear Oleg, Mikhail, dear Prof. Blaha,
Thank you for the quick answers!
It seems that the Alm (related to the "u") coefficient might be what I
need, because it refers to the "atomic-like" potential. Perhaps the
Blm coefficient, related to the "u-dot", is "small" in most cases,
also maybe it somehow represents the non-atomic (i.e. non-LCAO)
correction to the electronic state inside the MT sphere? I apologize
if calling "u" of LAPW as being "atomic" is wrong, but maybe it is not
totally wrong in the spirit of my problem. I am fine with approximate
numbers here, everything in the order of 80%-90% (say referring to the
final ARPES intensity) would be fine, I think. (The Alm of different
atoms would just control the amplitude and phase interference of the
spherical waves photoemitted from these atoms.)
Does that way of thinking make some sense?
Perhaps it is also the case, that a very large LCAO basis can explain
any band structure, but I think this is not the point, here the goal
is to simplify the problem.
In this physical problem, I cannot live without the complex
coefficients. This is easily understood in graphene, where the "dark
corridor" of ARPES results from the k-dependent phases of the
wave-functions on sites A and B.
Best,
Lukasz
On 2024-02-15 08:40, Peter Blaha wrote:
Hi,
I do not know too much about Wannerization and LCAO models.
However, I'd like to mention the PES program, which is included in
WIEN2k.
It uses the atomic cross sections (as you mentioned), but not the
wavefunctions, but the "renormalized" partial DOS. (This will omitt
the interstital and renormalize in particular the delocalized
orbitals).
It does NOT include phases (interference), but our experience is
quite good - although limited. Check out the PES section in the UG and
the corresponding paper by Bagheri&Blaha.
Regards
Am 15.02.2024 um 01:41 schrieb pluto via Wien:
Dear All,
I am interested to project WIEN2k band structure onto atomic
orbitals, but getting complex amplitudes. For example, for graphene
Dirac band (formed primarily by C 2pz) I would get two k-dependent
complex numbers A_C2pz(k) and B_C2pz(k), where A and B are the two
inequivalent sites, and these coefficients for other orbitals (near
the Dirac points) would be nearly zero. Of course, for graphene I
can write a TB model and get these numbers, but already for WSe2
monolayer TB model has several bands (TB models for WSe2 are
published but implementing would be time-consuming), and for a
generic material there is often no simple TB model.
Some time ago I looked at the WIEN2k wave functions, but because of
the way LAPW works, it is not a trivial task to project these onto
atomic orbitals. This is due to the radial wave functions, each one
receiving its own coefficient.
I was wondering if I can somehow get such projection automatically
using Wien2Wannier, and later with some Wannier program. I thought
it is good to ask before I invest any time into this.
And I would need it with spin, because I am interested with systems
where SOC plays a role.
The reason I ask:
Simple model of photoemission can be made by assuming coherent
addition of atomic-like photoionization, with additional k-dependent
initial band amplitudes/phases. One can assume that radial integrals
in photoemission matrix elements don't have special structure and
maybe just take atomic cross sections of Yeh-Lindau. But one still
needs these complex coefficients to allow for interference of the
emission from different sites within the unit cell. I think for a
relatively simple material such as WSe2 monolayer, the qualitative
result of this might be reasonable. I am not aiming at anything
quantitative since we have one-step-model codes for quantitative.
Any suggestion on how to do this projection (even approximately)
within the realm of WIEN2k would be welcome.
Best,
Lukasz
PD Dr. Lukasz Plucinski
Group Leader, FZJ PGI-6
Phone: +49 2461 61 6684
https://electronic-structure.fz-juelich.de/
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Peter Blaha, Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
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WWW: http://www.imc.tuwien.ac.at WIEN2k: http://www.wien2k.at
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