[Wien] LDA-GGA and van der Waals
tran at theochem.tuwien.ac.at
tran at theochem.tuwien.ac.at
Mon Mar 9 17:16:45 CET 2015
No. Formally, both LDA and GGA do not take into account van der Waals
interactions. vdW interactions are taken into account only with more
adanced functionals:
http://scitation.aip.org/content/aip/journal/jcp/141/7/10.1063/1.4893329
On Mon, 9 Mar 2015, Osama Yassin wrote:
> Dear Prof Blaha,
>
> With reference to the paper
>
> Calculation of the lattice constant of solids with semilocal functionals
>
> Philipp Haas, Fabien Tran, and Peter Blaha
>
> PHYSICAL REVIEW B79, 085104 2009
>
> For layred metal dichalcogenides (e. g. WS2), does it sound correct if the
> difference between the lattice constants obtained by LDA and that obtained
> GGA is equivalent to the lattice contraction due to van der Waals forces?
>
>
> Osama
> Department of Physics, Faculty of Science
> Taibah University, A-Madinah Al-Munawarh, K. Saudi Arabia
> A man would do nothing if he waited until he could do it so well that no one
> could find fault.
>
> On Sat, Mar 7, 2015 at 10:24 AM, Peter Blaha <pblaha at theochem.tuwien.ac.at>
> wrote:
> There is a misunderstanding: No, don't take a "mean" energy.
>
> Check also the corresponding charge. When it is large, it is a
> major
> component and needs an energy parameter close to this energy.
>
> In case.scf2 you can find under the line
> :EPH and :EPL
> the "mean" energy of the P-s states. If
> they are not close to -0.73
> (thats where you expand P-s), change the
> corresponding input value.
>
>
> For P-s, :EPL and :EPH are -1.34 and -0.43, mean of
> -0.89, fairly close to
> -0.73?
>
>
> Together with the large P-s charge in :EPL it tells you, that
> you should
> lower the P-s parameter in case.in1 to -1.34
> Whether one sets in addition a second l=0 Eparameter in case.in1
> depends on
> the E-separation between these EPL and EPH values, corresponding
> charges
> and the sphere radii (the larger the spheres: more probably
> yes).
> Here you have 0.9 Ry difference, but presumably the P-s charge
> in the upper E-window is
> very small and you have a very small spheres. Setting the two
> energies to those values might lead to ghostbands and at least
> at the beginning you
> moved one E-parameter up to +6 Ry. As I said previously, you may
> test it at the end
> and set the second Al-s line to 0.30 (no search), so that the
> actual E-parameter will be EF+0.2
>
> Other than P-s they are not close. Al-s has -7.24,
> -0.34, mean of -3.79,
> case.in1 has -7.65.
> O-s has -1.21, -0.30, mean is -0.75, while case.in1
> has -1.46. Similarly
> for Al-p and P-p.
>
>
> Again, there should be l=0 E-parameters close to -7.24 and 1.21,
> respectively.
> In addition there should be definitely a second Al-s line at
> 0.30, since there are
> "real" Al 3s states in the valence region.
>
> I had mostly read about a supercell with one full
> core hole. Some of these
> are certainly cells where I do not want to build a
> larger supercell than I
> have to. Is the HALF a core hole a better choice?
>
>
> Are you interested in XPS or in XAS. This is a VERY different
> process where the
> excited electron leave the bulk or stays whithin the bulk.
>
> For XPS you are interested just in ONE number (Al-2p
> ionizationpotential) and
> Slaters transition state concept with half a core hole applies.
>
> For XAS you want to simulate a spectrum for a system with one
> core hole and an additional e- in
> the valence band. Use (at least for insulators) a full core
> hole.
>
> Do I understand correctly that whether I use a HALF
> core-hole or a full one,
> I then do minimization of the ionic positions again?
>
>
> No. Electronic spectroscopy is a very fast process and the ions
> have no time to move
> around.
>
>
> The user-guide says "The energy cut-off specified in
> lstart during init lapw
> (usually -6.0 Ry) defines the separation
> into core- and band-states (the latter contain both,
> semicore and valence)."
> How do I get the Al 2p state into the core?
> Do I have to change the cut-off and use .lcore, or
> is there some way to move
> just the Al 2p state into the core?
>
>
> Besides an Energy (-X Ry), you can also specify a charge
> localization criterium
> (like 0.999), which will put all states with less charge inside
> sphere as valence.
> Checkout case.outputst to see how much charge each state has
> inside sphere:
> E-up(Ry) E-dn(Ry) Occupancy q/sphere
> core-state
> 1S -3.801989 -3.785331 1.00 1.00 0.9922 F
> 2S -0.236724 -0.003329 1.00 0.00 0.0675 F
>
>
>
> PS There was no "reply" button in the archive except
> "Reply via email". I
> could not find an answer as to how to reply to a
> post in either the Mail
> Archive FAQ, or the WIEN mail archive.
>
> Thanks,
> David
>
> ---------------------------------------------------------------------------
>
> At Thu, 05 Mar 2015 22:41:38 -0800, Peter Blaha
> wrote
> I think you have solved the problem very well.
>
> Due to the small P sphere and the fact, that P-s
> states are relatively
> high in energy, the two linearization energies must
> be quite well
> separated. (An alternative would have been to simply
> remove the second
> l=0 line for P and change to "3" lines only:
> 0.30 3 0 (GLOBAL E-PARAMETER WITH n
> OTHER CHOICES, global
> 1 0.30 0.000 CONT 1
> 1 -8.83 0.001 STOP 1
> 0 -0.73 0.002 CONT 1
>
> Two more checks towards the "end of the scf cycle":
> In case.scf2 you can find under the line :EPH and
> :EPL
> the "mean" energy of the P-s states. If they are not
> close to -0.73
> (thats where you expand P-s), change the
> corresponding input value.
>
> If the energy of the P-s states has gone down in
> energy at the end of the
> scf-cycles, you may
> checkout if you can go down with this second E-s
> input line from +6 back to
> 2.0
> or even
> back to 0.3 (sometimes such problems are
> temporary).
>
> PS: If you are interested in Al-2p XPS you should do
> Slaters transition
> state !
> Put Al 2p into the core and introduce HALF a core
> hole (compensated by a
> background).
> This gives much better core-eigenvalues that the
> plain DFT groundstate
> eigenvalues,
> typically lt. 1 % error as compared to 10 % error in
> comparison with
> experiment.
> In addition, final state screening effects are
> better accounted for.
>
>
> Am 06.03.2015 um 00:44 schrieb David Olmsted:
>
>
> Ghostbands: pushed energy range in case.in1 to 6.3,
> does this mean there is
> a problem?
>
> WIEN2k_14.2 (Release 15/10/2014)
> Quad-Core AMD Opteron(tm) Processor 2378
> Linux cluster
> Intel 11.1 compilers with mkl.
>
> The purpose of my computation is to compare
> predicted XPS spectra for Al 2p
> electon
> for different environments of the Al atom in the
> Al-P-O-H system.
>
> User: beginner! My first time using WEIN2k.
> Moderate amount of VASP work.
>
> Issue: ghostbands
>
> GGA-PBE, 48 atoms, K-mesh 6x6x4, no shift. Not
> spin-polarized.
> Initial cell and positions from relaxed GGA-PBE
> using VASP, same K-mesh.
>
> RMT from w2web StructGen (3% reduction)
> H 0.63
> O 1.17
> P 1.34
> Al 1.72
>
> RKmax 3.5 to get "effective RKmax" of 6.5 for O.
>
> rmt(min)*kmax = 3.50000
> gmin = 11.11111
> gmax = 20.00000
>
> ------- metavar_v.in0
> TOT XC_PBE
> (XC_LDA,XC_PBESOL,XC_WC,XC_MBJ,XC_REVTPSS)
>
> NR2V IFFT (R2V)
> 64 120 108 1.00 1 min IFFT-parameters,
> enhancement factor, iprint
> ---------
>
> For default -6 Ry cutoff for core states, charge was
> leaking out of RMT
> sphere
> for P 2p states. Final iteration in
> metavar_v.outputst:
> 14 350
> 14 1.85E-07 1.884765E+00 -8.645384E-01
> -8.645386E-01 1.72E-07
> -1.67E-08 1.707034E-01 1.707034E-01
> 1S -153.17082 -153.17082
> 2S -12.78682 -12.78682
> 2P* -9.19366 -9.19366
> 2P -9.12626 -9.12626
> 3S -1.02668 -1.02668
> 3P* -0.40735 -0.40735
> 3P -0.40342 -0.40342
>
> Cutoff set to -9.2 Ry. (Also tried leaving it at
> -6.0 Ry and touching
> .lcore. Similar results.)
>
> ===============================================================
> ---------------------------- Question
> -------------------------
> ===============================================================
>
> With the original case.in1 file, had messages for
> the P atom, L=0:
> (All these messages are from the first run of
> LAPW2.)
>
> metavar_v.scf2_1: QTL-B VALUE .EQ. 4951.54243 in
> Band of energy -6.46139
> ATOM= 2 L= 0
>
> increased 0.3 to 2.3 in case.in1, now:
>
> QTL-B VALUE .EQ. 1347.97207 in Band of energy
> -4.71553 ATOM= 2 L=
> 0
>
> increased it 4.3
>
> QTL-B VALUE .EQ. 602.53449 in Band of energy
> -2.14697 ATOM= 2 L=
> 0
>
> When I increased it to 6.3, no complaints.
>
> The initial scf run has completed with no warnings;
> the position
> minimization is still running.
>
> In the mailing list search, there are suggestions to
> increase the (upper)
> energy range to
> 1.3 or "even 2.0" Ry. That makes me worry about the
> fact that I had to
> increase it to a much
> larger value. Does this mean something is going
> wrong?
>
> ------------------------- End of question
> ------------------------
> =========== case.in1
> =============================================
> WFFIL EF=.1268392143 (WFFIL, WFPRI, ENFIL, SUPWF)
> 3.5 10 4 (R-MT*K-MAX; MAX L IN WF,
> V-NMT
> 0.30 4 0 (GLOBAL E-PARAMETER WITH n
> OTHER CHOICES, global
> APW/LAPW)
> 0 0.30 0.000 CONT 1
> 0 -7.65 0.001 STOP 1
> 1 0.30 0.000 CONT 1
> 1 -4.81 0.001 STOP 1
> 0.30 4 0 (GLOBAL E-PARAMETER WITH n
> OTHER CHOICES, global
> APW/LAPW)
> 1 0.30 0.000 CONT 1
> 1 -8.83 0.001 STOP 1
> 0 -0.73 0.002 CONT 1
> 0 6.30 0.000 CONT 1
> 0.30 3 0 (GLOBAL E-PARAMETER WITH n
> OTHER CHOICES, global
> APW/LAPW)
> 0 -1.46 0.002 CONT 1
> 0 0.30 0.000 CONT 1
> 1 0.30 0.000 CONT 1
> 0.30 3 0 (GLOBAL E-PARAMETER WITH n
> OTHER CHOICES, global
> APW/LAPW)
> 0 -1.46 0.002 CONT 1
> 0 0.30 0.000 CONT 1
> 1 0.30 0.000 CONT 1
> 0.30 3 0 (GLOBAL E-PARAMETER WITH n
> OTHER CHOICES, global
> APW/LAPW)
> 0 -1.46 0.002 CONT 1
> 0 0.30 0.000 CONT 1
> 1 0.30 0.000 CONT 1
> 0.30 3 0 (GLOBAL E-PARAMETER WITH n
> OTHER CHOICES, global
> APW/LAPW)
> 0 -1.46 0.002 CONT 1
> 0 0.30 0.000 CONT 1
> 1 0.30 0.000 CONT 1
> 0.30 3 0 (GLOBAL E-PARAMETER WITH n
> OTHER CHOICES, global
> APW/LAPW)
> 0 -1.46 0.002 CONT 1
> 0 0.30 0.000 CONT 1
> 1 0.30 0.000 CONT 1
> 0.30 3 0 (GLOBAL E-PARAMETER WITH n
> OTHER CHOICES, global
> APW/LAPW)
> 0 -1.46 0.002 CONT 1
> 0 0.30 0.000 CONT 1
> 1 0.30 0.000 CONT 1
> 0.30 1 0 (GLOBAL E-PARAMETER WITH n
> OTHER CHOICES, global
> APW/LAPW)
> 0 0.30 0.000 CONT 1
> 0.30 1 0 (GLOBAL E-PARAMETER WITH n
> OTHER CHOICES, global
> APW/LAPW)
> 0 0.30 0.000 CONT 1
> 0.30 1 0 (GLOBAL E-PARAMETER WITH n
> OTHER CHOICES, global
> APW/LAPW)
> 0 0.30 0.000 CONT 1
> 0.30 1 0 (GLOBAL E-PARAMETER WITH n
> OTHER CHOICES, global
> APW/LAPW)
> 0 0.30 0.000 CONT 1
> K-VECTORS FROM UNIT:4 -12.2 1.5 250 emin
> / de (emax=Ef+de) /
> nband #red
>
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>
> --
> -----------------------------------------
> Peter Blaha
> Inst. Materials Chemistry, TU Vienna
> Getreidemarkt 9, A-1060 Vienna, Austria
> Tel: +43-1-5880115671
> Fax: +43-1-5880115698
> email: pblaha at theochem.tuwien.ac.at
> -----------------------------------------
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