[Wien] Large difference in calculated and experimental EFG
Ramsewak Kashyap
kashyaprs89 at gmail.com
Tue Mar 19 09:40:49 CET 2019
Sorry sir,
It has 24 non equivalent site with 32 atoms in 2x2x2 cell and RKmax is 7.5
and 100 k-points and Ti replaced by Ta
Convergence criteria- ec 0.001 cc 0.001 fc 1mRy/bohr
Similarly for 3x3x2 supercell 48 non equivalent site and same condition
On Tue 19 Mar, 2019, 12:02 PM Peter Blaha, <pblaha at theochem.tuwien.ac.at>
wrote:
> I guess you said it is TiNi.
>
> How can a 2x2x2 supercell have 24 atoms ? This implies it has 3 atoms in
> the original cell, but that cannot be TiNi.
>
> Even more puzzling: 3x3x2 times 3 is for sure not 48 atoms ????
>
> PS: I'd definitely go first to about 60 atoms cells, later on test
> convergence with 120 atoms cells !!!
>
> More problems: What is your RKmax ? You definitely should increase it
> from the default 7.0 ! What is your k-mesh ?? It is a metal !
>
> And finally: Is it know whether the Ta sits on a substitutional site ?
> Which one, Ti or Ni ? Or is it some interstital site ??
>
> Most likely this is not well known experimentally. So several different
> model calculations may be necessary and you can use E-tot (lowest) as
> well as the EFG/eta to decide which structural model is the correct one.
>
> Am 19.03.2019 um 05:56 schrieb Ramsewak Kashyap:
> > In 2x2x2 supercell, total no. of atoms was 24 and it gave EFG value 6.5
> > 10**21V/m**2 with eta 0.81.
> > I have also calculated for 3x3x2 supercell has 48 atoms and it gave EFG
> > value 6.3 10**21V/m**2 with eta 0.88
> >
> > While experimental is about EFG is 4.4 with eta 0.60..
> >
> > On Mon 18 Mar, 2019, 7:39 PM Peter Blaha, <pblaha at theochem.tuwien.ac.at
> > <mailto:pblaha at theochem.tuwien.ac.at>> wrote:
> >
> > Most importantly: You talked about a 2x2x2 supercell ???
> >
> > We don't know how big your original cell was, but a 16 atome cell
> > with 1
> > T is not an impurity as measured in PAC.
> > How many atoms are in this supercell ???
> >
> > You must probably increase the supercell size and check convergence
> of
> > the EFG.
> >
> > On 3/18/19 1:15 PM, Stefaan Cottenier wrote:
> > > If the goal is to have a EFG that is a predictive as possible for
> > > experiment, then it is advised to take the experimental cell
> > parameters
> > > (but with position optimization).
> > >
> > > If that EFG does not agree with experiment, then this is a
> > trigger to
> > > search further. There can be many reasons (assuming both the
> > experiment
> > > and the calculation are correctly done):
> > >
> > > * You have an unusually sensitive case, where small details that
> > > usually do not matter do affect the EFG
> > > * The effect of temperature might be unusually large (your
> > calculation
> > > is at 0 K)
> > > * Maybe the Ta atom is associated with a defect (vacancy,
> oxygen,…)
> > > and the experiment measures that complex.
> > > * …
> > >
> > > Stefaan
> > >
> > > *From:*Wien <wien-bounces at zeus.theochem.tuwien.ac.at
> > <mailto:wien-bounces at zeus.theochem.tuwien.ac.at>> *On Behalf Of
> > > *Ramsewak Kashyap
> > > *Sent:* Monday, March 18, 2019 12:41 PM
> > > *To:* A Mailing list for WIEN2k users
> > <wien at zeus.theochem.tuwien.ac.at
> > <mailto:wien at zeus.theochem.tuwien.ac.at>>
> > > *Subject:* Re: [Wien] Large difference in calculated and
> > experimental EFG
> > >
> > > atomic positions optimization means force relaxation.. I have
> > did that.
> > > but I am asking about cell parameter optimization. Is it
> > necessary for
> > > .cif file getting form COD??
> > >
> > > Thanks
> > >
> > > On Mon, Mar 18, 2019 at 4:55 PM Stefaan Cottenier
> > > <Stefaan.Cottenier at ugent.be <mailto:Stefaan.Cottenier at ugent.be>
> > <mailto:Stefaan.Cottenier at ugent.be
> > <mailto:Stefaan.Cottenier at ugent.be>>> wrote:
> > >
> > > Yes, optimization of the atomic positions is absolutely
> > necessary to
> > > have a meaningful value for Vzz and eta in a supercell.
> > >
> > > Stefaan
> > >
> > > *From:*Wien <wien-bounces at zeus.theochem.tuwien.ac.at
> > <mailto:wien-bounces at zeus.theochem.tuwien.ac.at>
> > > <mailto:wien-bounces at zeus.theochem.tuwien.ac.at
> > <mailto:wien-bounces at zeus.theochem.tuwien.ac.at>>> *On Behalf Of
> > > *Ramsewak Kashyap
> > > *Sent:* Monday, March 18, 2019 12:23 PM
> > > *To:* A Mailing list for WIEN2k users
> > > <wien at zeus.theochem.tuwien.ac.at
> > <mailto:wien at zeus.theochem.tuwien.ac.at>
> > > <mailto:wien at zeus.theochem.tuwien.ac.at
> > <mailto:wien at zeus.theochem.tuwien.ac.at>>>
> > > *Subject:* [Wien] Large difference in calculated and
> > experimental EFG
> > >
> > > Hi Wien2k users,
> > >
> > > I am doing EFG calculation for TiNi monoclinic phase, but I am
> > > getting large difference in Calculated and measured value, I
> have
> > > taken parameters from COD, then make 2x2x2 supercell and
> > replace one
> > > Ti with Ta atom... is structural optimization is necessary??
> and
> > > eta value was also quite large as compare to measured value.
> > >
> > > --
> > >
> > > Ramsewak Kashyap
> > > Saha Institute of Nuclear Physics
> > > 9473811023
> > >
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> > >
> > > --
> > >
> > > Ramsewak Kashyap
> > > Saha Institute of Nuclear Physics
> > > 9473811023
> > >
> > >
> > > _______________________________________________
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> >
> > --
> >
> > P.Blaha
> >
> --------------------------------------------------------------------------
> > Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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> --
> --------------------------------------------------------------------------
> 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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