[sdpd] Re: Advices on Anisotropic Broadening on Size and Strain

["L_Solovyov" <l_solovyov...@yahoo.com>]

--- In sdpd...@yahoogroups.com, Tay Yee Yan <one_twinklestar...@y...> wrote:
> Hi All:
> 
> I just posted some problems on the tutorial of the
> refinement of sodium-para-hydroxybenoate. For this
> materials, the anisotropic broadening is mainly due to
> strain. However, there are some materials that have
> anisotropic broadening due to size. May I know in the
> first place, how do you actually differentiate if the
> materials is due to anisotropic strain or size? If
> both broadening occur in the materials, how can I
> identify them?
> 

The peak broadening increases with diffraction angle as 1/cos(Theta) 
in the case size effect and as tan(Theta) in the case of strain. This 
is valid for both isotropic and anisotropic broadening. To decide 
which effect is actually present one may try refinement with aniso-
srain, aniso-size or both size and strain corrections and then 
compare the results. The anisotropic size and strain broadening 
components are resolvable for diffraction patterns of good enough 
quality.

Best regards,
Leonid






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