[Wien] SCF and symmetry
Peter Blaha
pblaha at theochem.tuwien.ac.at
Tue Dec 1 17:13:37 CET 2015
As Laurence said, you cannot compare energies with different RKmax.
Wien2k truncates RKMAX, if this would lead to matrices larger than
NMATMAX (specified during installation with siteconfig) to avoid
overloading/paging your machine (and making it "unusable").
In addition, since a case with complex matrices (no inversion) needs
twice the memory, it will reduce the effective matrix-size by another
factor of sqrt(2). Thus you got the different RKmax.
a) NEVER ignore WARNINGS (unless you read and UNDERSTAND the :WAR
message and it is non-critical for your case).
b) You mentioned "2 molecules ...." previously. If this contains H with
small RMTs, RKmax=3 is enough. Reduce it in case.in1(c).
Read http://www.wien2k.at/reg_user/faq/rkmax.html
On 12/01/2015 02:02 PM, Laurence Marks wrote:
> Peter may be busy.....
>
> The RKM value is critically important, and you cannot compare different
> values. I guess you are running on a single node without mpi, and the
> RKM value has been automatically reduced to avoid going beyond the
> memory limits (set via NMATMAX). Unless you have small minimum RMT's
> such as for H (~0.5) an RKM value around 3 is way too small. You need to
> repair this, either using more cores & mpi or something else.
>
> You sound like you have some DFT experience, but I suspect not much with
> WIEN2K. Have you tried simpler systems first?
>
> ---
> Professor Laurence Marks
> Department of Materials Science and Engineering
> Northwestern University
> http://www.numis.northwestern.edu
> Corrosion in 4D http://MURI4D.numis.northwestern.edu
> Co-Editor, Acta Cryst A
> "Research is to see what everybody else has seen, and to think what
> nobody else has thought"
> Albert Szent-Gyorgi
>
> On Dec 1, 2015 01:40, "Bruno Landeros" <brunolanderos at hotmail.com
> <mailto:brunolanderos at hotmail.com>> wrote:
>
> Yes, there was a WARNING in the total energies.
>
> RKM for the NOSYM is 3.18 and 3.57 for the symmetric.
> Is this the reason? Should I increase it?
>
> Enviado desde Correo de Windows
>
> *De:* pblaha at theochem.tuwien.ac.at <mailto:pblaha at theochem.tuwien.ac.at>
> *Enviado el:* martes, 1 de diciembre de 2015 01:23 a. m.
> *Para:* wien at zeus.theochem.tuwien.ac.at
> <mailto:wien at zeus.theochem.tuwien.ac.at>
>
> One more thought:
>
> Since these are large cells and one has inversion and the other not,
> could it be that due to size-limitations of NMATMAX the complex case
> (no
> symmetry) used a much lower RKMAX ? You also should see a WARNING in
> your total energies.
>
> grep :RKM case.scf for the two cases.
>
> On 12/01/2015 08:03 AM, Bruno Landeros wrote:
> > The first time I generated the Nosymm structure file was by using
> the 76
> > posiciones generated by a first symmetric scf calculation (no
> coordinate
> > optimization), so the same coordinates where used in both cases.
> >
> > To be sure, I run again the Nosymm structure file but accepted
> the new
> > structfile suggested by the SGROUP program, which detected the
> corrected
> > symmetry and this gave the energy I just mentioned here, so in
> principle
> > they are equivalent.
> >
> > Would you like me to send you the case.struct files with the
> > specifications I gave with init_lapw?
> >
> > Enviado desde Correo de Windows
> >
> > *De:* pblaha at theochem.tuwien.ac.at
> <mailto:pblaha at theochem.tuwien.ac.at>
> <mailto:pblaha at theochem.tuwien.ac.at>
> > *Enviado el:* martes, 1 de diciembre de 2015 12:53 a. m.
> > *Para:* wien at zeus.theochem.tuwien.ac.at
> <mailto:wien at zeus.theochem.tuwien.ac.at>
> > <mailto:wien at zeus.theochem.tuwien.ac.at>
> >
> > No. This is a huge E-difference which must come from something very
> > severe. Did you compare the distances in the 2 case.outputnn file or
> > compare the structures in xcrysden.
> >
> > On 12/01/2015 07:37 AM, Bruno Landeros wrote:
> > > Dear Peter:
> > >
> > > Yes, my mistake. First energy (no symmetry) is
> > > -5752.55335845 Ry.
> > > while second energy is
> > > -5752.17735109 Ry.
> > >
> > > Since cell parameters are note small (12.994513, 25.002400,
> 17.381701
> > Bohr)
> > > and I was testing convergence I asked for just 1 K point in
> both cases.
> > > May be this the origin of the discrepancy?
> > >
> > > Greetings,
> > >
> > > Bruno
> > >
> > >
> > > Enviado desde Correo de Windows
> > >
> > > *De:* pblaha at theochem.tuwien.ac.at
> <mailto:pblaha at theochem.tuwien.ac.at>
> <mailto:pblaha at theochem.tuwien.ac.at>
> > > *Enviado el:* martes, 1 de diciembre de 2015 12:16
> a. m.
> > > *Para:* wien at zeus.theochem.tuwien.ac.at
> <mailto:wien at zeus.theochem.tuwien.ac.at>
> > > <mailto:wien at zeus.theochem.tuwien.ac.at>
> > >
> > > The energies you posted are identical !
> > >
> > > Anyway: I hope you did not just copy the case.klist file from
> the low to
> > > the high-symmetry case ??
> > >
> > > Otherwise: send me your 2 struct files together with the
> description of
> > > the chosen calculational parameters (everything which is
> non-default) to
> > > my private email.
> > >
> > > Am 01.12.2015 um 03:00 schrieb Bruno Landeros:
> > > > I'm studying a molecular crystal in which two different
> molecules form
> > > > an 1:1 adduct. There are 2 molecules of each kind (4 in
> total) in the
> > > > unit cell. There are 19 atoms in the asymmetric unit, and
> since it
> > > > belongs to the P21/c spacegroup, a total of 76 atoms are
> contained in
> > > > the unit cell. I was trying to find a possible mistake when
> > calculating
> > > > interaction energies and I found the next problem:
> > > >
> > > > If I calculate the SCF by manually inserting the 76
> positions and
> > giving
> > > > it a P1 symmetry the energy converged to
> > > > -5752.17735109 Ry.
> > > >
> > > > If I calculate the SCF by inserting the 19 atoms of the
> asymmetric
> > unit
> > > > with the correct symmetry and let the program to generate
> the rest of
> > > > the positions (which where exactly the same as when inserted
> > manually),
> > > > the same functional, same RMT, same K points and same
> convergence
> > > > criteria the energy converged to
> > > > -5752.17735109 Ry.
> > > >
> > > > Transforming the energy difference between the 2 calculations
> > gives 195
> > > > kcal/mol. The same happened when doing the same for other
> systems.
> > > >
> > > > My question is, ¿shouldn't I get the same energy in both
> calculations
> > > > since it's the same system, same coordinates and the input was
> > prepared
> > > > equally except for the symmetry?
> > > > Since I'm trying to calculate interaction energies using
> different
> > > > subsystems, some with and some without symmetry, this is a
> relevant
> > > > question to my research.
> > > >
> > > >
> > > > Greetings,
> > > >
> > > > Bruno L
> > > >
> > > >
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> > > --
> > >
> >
> --------------------------------------------------------------------------
> > > Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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> > --
> >
> > P.Blaha
> >
> --------------------------------------------------------------------------
> > Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> > Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
> > Email: blaha at theochem.tuwien.ac.at
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> P.Blaha
> --------------------------------------------------------------------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
> Email: blaha at theochem.tuwien.ac.at
> <mailto:blaha at theochem.tuwien.ac.at> WIEN2k: http://www.wien2k.at
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--
P.Blaha
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Email: blaha at theochem.tuwien.ac.at WIEN2k: http://www.wien2k.at
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