Re: Fourier Transform in crystallography



Hi, Zaw,

I must own up here that my understanding is largely theoretical. I have
just looked over the shoulder of someone who knew how to operate
Sheldrake's program: Shelx, if I remember correctly.

> Thanks you for your reply. But I would like to know in deeply about
> contour and surface map of FT and DF(difference fourier). Can I get any
> informations in maps.

Yes.

> For FT it is ok to get the position of nucleus?

In principle. How else are you going initially to find out the position
of the nucleus? Subsequently you will use the least-squares procedure
but in any case the electron density always has a sharply-defined local
maximum at the nuclear positions.

> What can we know from DF? And both from?

> Thanks for your reply answer. I encountered one thing that in my
> contour the peak of nucleus is in opposite direction I mean not
> dominant but entering inside. I don't know why. Could you instruct me
> for it what it means?


I'm not quite sure what you mean by 'entering inside'? Do you mean
'going negative'? If so, are you sure that you have correctly
identified the nucleus in question? For example, perhaps you think it's
an oxygen with 8 electrons, but it is in fact a nitrogen with 7
electrons.

Cheers,

Zigoteau.

.

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