For a difference density it is of course necessary that you treat the
same states in the solids and in the atom.
While in an atom this is fairly simple, because each state is classified
by n,l,m (or kappa), for the solid we are missing the "n". We know
easily the "l" (s,p,d,f), but not the principal quantum number n (like
4p or 5p).
This can be only be done by comparising with the atom, via the
"knowledge" what a chemist would call "valence and core" states and via
the energies of these states.
a) execute: x lstart -sigma
b) This creates a case.inst_sigma input file, where the "P" indicates
to you, which atomic densities are plotted.
c) Look into case.outputst to see their energies (and in particular
those of lower lying states (semi-core states) which have a "T"
indicating that they are included in the solid as "valence" and some of
them must be cut away.
d) now look at your scf1 file (both the E-parameters as you showed us,
but also the eigenvalues. Sometimes also the band-ranges in case.output2
are helpful.:
> ATOMIC SPHERE DEPENDENT PARAMETERS FOR ATOM Ce
> :e__0001: OVERALL ENERGY PARAMETER IS 0.5943
> OVERALL BASIS SET ON ATOM IS LAPW
> :E2_0001: E( 2)= 0.5943
> APW+lo
> :E2_0001: E( 2)= -6.9944 E(BOTTOM)= -7.002 E(TOP)= -6.987
1 2 170
> LOCAL ORBITAL
> :E0_0001: E( 0)= 0.5943
> APW+lo
> :E0_0001: E( 0)= -1.8665 E(BOTTOM)= -2.558 E(TOP)= -1.175
4 5 176
> LOCAL ORBITAL
> :E1_0001: E( 1)= 0.9943
> APW+lo
> :E1_0001: E( 1)= -0.4363 E(BOTTOM)= -1.448 E(TOP)= 0.575
3 4 197
> LOCAL ORBITAL
> :E3_0001: E( 3)= 0.6959 E(BOTTOM)= 0.466 E(TOP)= 0.925
0 1 123
> APW+lo
There should be Ce-d states around -7 Ry. Compare to the outpust file
and you should see that these are 4d states (they are a bit lower in the
atom) and thus "not valence", so they sould be cut away.
You can do the same for Ce-s (5s) and finally 5p. The latter are at -1.6
in the atom, but according to your list at -0.4 in the solid.
e) So look again at the eigenvalues of case.output1 or the band ranges
in output2 and you should find a solution: most likely your emin
should be around -0.2 or so, i.e. in the "gap" between the real valence
states (B-sp Ce-4f,5d,6sp) and the semicore states as identified above.
PS: In some cases, the "automatic" procedure with "x lstart -sigma" may
not work. Take a Ce-oxide, there will be O-2s states at LOWER energy
than these Ce-5p states and you CANNOT select an EMIN, which "keeps" the
O-2s but cuts away the Ce-5p. In such cases you have to explicitly
include / exlude certain states in the atom (eg. edit case.inst_sigma
and replace the "P" by "N" for the O-2s states, rerun:
lstart lstart.def (where lstart.def should contain: case.inst_sigma,
not just case.inst).
Am 27.04.2020 um 04:38 schrieb Ding Peng:
Dear WIEN2k experts,
I am trying to calculate the difference electron density of CeB6, which has a
space group of Pm-3m, by WIEN2k (16.04). After I finished running SCF cycles (I
used non-magnetic calculation GGA+U calculation, runsp_c_lapw, by forcing the
magnetic moment in a spin-polarised setup to zero), I followed the electron
density calculation process:
1) check case.scf1, it shows
---------------------------------------------------------------------
LDA+U potential added for atom type 1 L= 3 spin up
:LMAX-WF: 10 Non-Spherical LMAX: 4
ATOMIC SPHERE DEPENDENT PARAMETERS FOR ATOM Ce
:e__0001: OVERALL ENERGY PARAMETER IS 0.5943
OVERALL BASIS SET ON ATOM IS LAPW
:E2_0001: E( 2)= 0.5943
APW+lo
:E2_0001: E( 2)= -6.9944 E(BOTTOM)= -7.002 E(TOP)= -6.987 1 2 170
LOCAL ORBITAL
:E0_0001: E( 0)= 0.5943
APW+lo
:E0_0001: E( 0)= -1.8665 E(BOTTOM)= -2.558 E(TOP)= -1.175 4 5 176
LOCAL ORBITAL
:E1_0001: E( 1)= 0.9943
APW+lo
:E1_0001: E( 1)= -0.4363 E(BOTTOM)= -1.448 E(TOP)= 0.575 3 4 197
LOCAL ORBITAL
:E3_0001: E( 3)= 0.6959 E(BOTTOM)= 0.466 E(TOP)= 0.925 0 1 123
APW+lo
ATOMIC SPHERE DEPENDENT PARAMETERS FOR ATOM B
:e__0002: OVERALL ENERGY PARAMETER IS 0.5943
OVERALL BASIS SET ON ATOM IS LAPW
:E0_0002: E( 0)= 0.5943
APW+lo
:E1_0002: E( 1)= 0.5943
APW+lo
---------------------------------------------------------------------
2) I choose the default value Emin = -1 and rerun LAPW2 calculation
3) run lstart -sigma to calculate the superposed atomic electron density
4) run lapw5 and set the option "DIFF" in case.in5
The result difference electron density map was presented by Xcrysden. I found
very strong electron accumulation (delta rho is positive) near the core of Ce
ions and electron depletion(delta rho is negative) near the core of B ions.
My questions are:
1) Does this result makes sense? Because Ce3+ is cation, which should tend to
lose electrons, and therefore delta rho should be negative near the core of Ce.
This contradicts to my difference electron density map.
2) Is the superposed atomic electron density equivalent to the superposed
atomic electron densities from independent atomic model (IAM)? Or it is
equivalent to the superposition of the atomic electron densities of ions?
3) Is it correct to set Emin = -1? I had read the past discussions about this
topic from the Wien2k email list, but still have no idea how to determine Emin
based on the results in case.scf1.
Look forward to the answers.
Many thanks,
Ding
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