[Wien] LDA-GGA and van der Waals

Osama Yassin oyassin63 at gmail.com
Mon Mar 9 17:09:08 CET 2015


Dear Prof Blaha,

With reference to the paper




*Calculation of the lattice constant of solids with semilocal
functionalsPhilipp 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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