[Wien] temperature influence on EFGs calculations

[Rocquefelte]

OK. Now I better understand your question.
Indeed the magnetic ordering is playing an essential role in the 
temperature dependence of Mossbauer parameters.

Switching to  TEMP with a fixed value will not help you in the present 
case, because you must consider the temperature effect by calculating 
the Mossbauer parameters for the antiferromagnetic low temperature 
magnetic order and the paramagnetic room temperature one. However, we 
cannot do a calculation for a paramagnetic order (which is dynamic).

Some years ago we had a similar problem for the modelling of the 
temperature effect of optical and magnetic properties of CuO. It was not 
so different to your problem except that the Neel temperature is 
significantly higher (TN = 230 K). We were able to reproduce the 
evolution of the electric field gradient (deduced from NMR exp.) by 
considering "snapshots" of the magnetic phases of CuO in which magnetic 
disorder were created. Our strategy was thus to neglect the dynamical 
effects of the temperature and to consider only the progressive growth 
of magnetic disorder in CuO. It was a very efficient approximation which 
were able to reproduce not only the temperature effect on the magnetic 
and EFG data, but also the optical properties.

Here is the reference of this paper. I hope it can help you.

http://iopscience.iop.org/0953-8984/22/4/045502/

Best Regards

Xavier
P.S.: If you need I can send you a PDF copy of the paper.






Le 7/17/2013 10:32 AM, abdel Mar.. a écrit :
> thank you Xavier for your replay
>
> As you know Mossbauer parameters vary with temperature
> my Mossbauer parameters are measured at room temperature.
> how can we relate this measure (at room temperature) to the calculated 
> value at (0k).
>
> for example : my material is paramagnetic  at room temperature, 
> antiferromagnetic at low temperature < 30K.
> my measure is at room temperature, so my calculation will be for 
> antiferro. case. i'm lost at this stageEmoji
>
> Regards
> A
>
> ------------------------------------------------------------------------
> Date: Wed, 17 Jul 2013 09:57:19 +0200
> From: xavier.rocquefelte at cnrs-imn.fr
> To: wien at zeus.theochem.tuwien.ac.at
> Subject: Re: [Wien] temperature influence on EFGs calculations
>
> Which temperature effect do you want to consider?
> Indeed, the effect of temperature on the atomic structure is usually 
> the more important one for EFGs...
> Thus one way to consider the temperature effect on these properties is 
> simply to consider different atomic structures refined for different 
> temperatures (volume expansion...).
>
> Best Regards
>
> Xavier
>
>
>
> Le 7/17/2013 9:44 AM, abdel Mar.. a écrit :
>
>     Dear Wien2k users
>
>     is there a way to include the temperature effetc in the
>     calculation of the Mossbauer parameters ( EFGs, RTO).
>
>     may be with in case.in2?: with switching to  TEMP with a fixed value?
>     TEMP 0000 (GAUSS, ROOT, TEMP, TETRA, ALL eval)
>
>     Best regards
>
>     A
>
>
>
>
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