[cctbxbb] Adding more parameters to xray::scatterer for anharmonic thermal displacements

[Pavel Afonine]

Sounds fine to me with a caveat that perhaps this is an opportunity to 
rationalize handling of ADPs in xray::scatterer. Currently we have 
isotropic, anisotropic, mixture, TLS, TLS with individual isotropic 
component, all scattered across different pieces of code. I have tons of 
code that deal with this externally outside xray::scatterer (even 
outside xray.structure !!) and that needs to be rationalized and 
centralized in some way. Otherwise we might be adding to the pile of 
ad-hocs. Of course that requires time to actually do it and therefore 
some planning (I wouldn't be able to dive into this say today or next 
week, or even next month).

Needless to say that it would be nice to have anharmonic B-factors in 
phenix.refine as well when it comes to refinements at ultra-high 
resolution (as well as other smart ADP restraints that smtbx has!).

All the best,
Pavel

On 8/21/18 18:58, Luc J. Bourhis wrote:
> Hi,
>
> we are working with Michal Chodkiewicz (Warsaw University) to add
> anharmonic thermal tensors to smtbx refinement. I was thinking to add
> one pointer to xray::scatterer, which can be NULL. When it is not so,
> it would point to an object which can compute the value and the
> derivatives for that thermal factor. That means we would have a base
> class with virtual methods, but I would say that is our problem!
>
> The issue for the rest of the cctbx community is the extra storage of
> that pointer in that class. Would that be all right? I remember quite a
> few years ago Ralf saying he wanted to replace the ADP's by a pointer
> to an external storage to save space. Our idea is along the same line.
>
> Best wishes,
>
> Luc
>
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