[Wien] SCF and symmetry
Peter Blaha
pblaha at theochem.tuwien.ac.at
Tue Dec 1 08:23:07 CET 2015
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>
> *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>
>
> 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>
> > *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>
> >
> > 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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> > --
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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 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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