[Wien] EFG: theory Vs experiment for a case

[Laurence Marks]

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 enter the Ti RMT and give you pseudo-d's.

On Tue, Dec 18, 2018 at 12:38 PM Ashwani Kumar <ashwani.ism at gmail.com>
wrote:

> 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 x 10^21 V/m2 (calculated from TDPAC results). STO has cubic
> lattice so no efg and no assymetry  parameter (for both wien2k and TDPAC)
> but defect STO structure showed very pure hyperfine interactions with
> assymetry parameter : 0.52. So i am not having confidence over my wien2k
> calculation because :
> 1. i am getting assymetry parameter =0
> 2. Negative EFG which i understood from previous answers that negative
> sign indicates the rate of decrease of z-component of EF wrt to distance.
>
> Am i missing something?,
> Calculation parameters are :Supercell (3x2x2) STO with doped Hf atom, PBE,
> KGEN:200, rkmax: 7.0,
>
> thanks,
> A. Kumar
>
> On Fri, Dec 14, 2018 at 11:02 PM Ashwani Kumar <ashwani.ism at gmail.com>
> wrote:
>
>> Hi,
>>   i have calculated EFG  the defect structure of crystalline system from
>> experimental data from PAC spectroscopy. Then using WIEN2K (crystal
>> structure--> supercell--> defect introduced), EFG is calculated.
>> 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.
>>
>> thanks,
>> A. Kumar
>>
>

-- 
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu ; Corrosion in 4D: MURI4D.numis.northwestern.edu
Partner of the CFW 100% program for gender equity, www.cfw.org/100-percent
Co-Editor, Acta Cryst A
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