[Wien] Large difference in calculated and experimental EFG

[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>
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> *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>
> > *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>> 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>> *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>>
> >     *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
> >
> >     _______________________________________________
> >     Wien mailing list
> >     Wien at zeus.theochem.tuwien.ac.at <mailto:
> Wien at zeus.theochem.tuwien.ac.at>
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> >
> http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
> >
> >
> > --
> >
> > 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
> 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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