Thanks everyone for the warm discussion. I started fresh again with the
STO.
Dear Dr. Laurence, can you share the reference's information.
Yes that's true, present literatures focuses on the Oxygen vacancy in STO
created due to controlled synthesis parameters (like partial pressure of
oxygen).
> I don't know if one can trust eta from the PAC results ?
In principle there is no objection. If it is a sufficiently clean experiment
(good statistics, not too many different sites, sufficiently strong EFGs,...)
then TDPAC can get eta with an error bar better than 0.1.
> > To what %
I remain shocked that the majority of the recent STO literature has ignored
the older, more careful literature. The dominant point defect is the
valence neutral divacancy SrO, particularly under oxidizing conditions. I
strongly suggest you research the papers with real measurements, not those
with
As an addendum to previous comments by the experts I strongly recommend
to always ask (and answer) yourself the question:
what symmetries does the experimental result imply, and what symmetries
are present in my model?
You state that samples prepared in a precedure 'where synthetic
parameters
System under study is SrTiO3 doped with Hf-181
tdpac probe for TDPAC spectroscopy by thermal equillibriation method (1250
C for >12 hours). the doping is substitutional as Hf(IV) and Ti(IV) has
nearby ionic radius and same oxidation state. Bulk STO shows no efg, no
tefaan
From: Wien On Behalf Of Ashwani Kumar
Sent: Tuesday, December 18, 2018 7:39 PM
To: wien
Subject: Re: [Wien] EFG: theory Vs experiment for a case
hi,
thanks for reply. the assymetry parameter, (Vxx-Vyy)/Vzz, is zero (wien2k
calculation) whereas i got 0.52 from TDPAC (Time dependent per
The presence of an EFG and of a non-zero eta is first of all a symmetry
property.
If you get in exp eta=0.5, but in theory eta=0.0 (by symmetry ?), it
simply means that the Hf impurity in PAC is not at the same position or
does not have the same environment than the Hf in your simulations.
With STO PBE is too covalent. For many properties you need to use either
-eece (my preference), +U or a full hybrid. In addition the default RMT for
Sr in STO is normally too large, something like 2.05 is better.
N.B., be careful not to have the Ti RMT too large as then the tails of the
O 2p
hi,
thanks for reply. the assymetry parameter, (Vxx-Vyy)/Vzz, is zero
(wien2k calculation) whereas i got 0.52 from TDPAC (Time dependent
perturbed angular correlation) spectroscopy for a SrTiO3 (STO) defect
structure. EFG component is -1.63 x10^21 V/m2 (wien2k, lapw2 -efg) and i
obtained 1.69
> From: Ashwani Kumar Friday, December 14, 2018 6:33
> Exper. Calculated : 1.69 x 10^21 V/m2 whereas wien2k calculation: -1.66 x
> 10^21 V/m2 (crude value still have to do lapw2 -efg) on probe atom. Wien2k
> calculation shows negative value. is there any significance of the negative
> sign
>
Most EFG experiments measure the absolute value only, hence you usually do not
know the experimental sign.
The meaning of the sign is the same as for any derivative: a negative Vzz means
that d Ez/dz is negative: the value of the z-component of the electric field
becomes *smaller* if you go
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