[Wien] Questions about difference electron density map
Ding Peng
ding.peng at monash.edu
Mon Apr 27 10:41:21 CEST 2020
Dear Prof Peter Blaha,
Thank you very much for your detailed explanation.
Many thanks,
Ding
On Mon, 27 Apr 2020 at 4:25 pm, Peter Blaha <pblaha at theochem.tuwien.ac.at>
wrote:
> 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 E
> <https://www.google.com/maps/search/t+still+have+no+idea+how+to+determine+E?entry=gmail&source=g>min
> based on the results in case.scf1.
> >
> >
> > Look forward to the answers.
> >
> > Many thanks,
> > Ding
> >
> > _______________________________________________
> > Wien mailing list
> > Wien at zeus.theochem.tuwien.ac.at
> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
> > SEARCH the MAILING-LIST at:
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> >
>
> --
> Peter Blaha
> Inst.Materials Chemistry
> TU Vienna
> Getreidemarkt 9
> A-1060 Vienna
> Austria
> +43-1-5880115671
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
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