James - you are fantastic!
This is so educational..
Eleanor
On 11/02/2011 02:36 AM, James Holton wrote:
> On Tue, Nov 1, 2011 at 3:32 PM, Ivan Shabalin<[log in to unmask]> wrote:
>> Does that mean, that with Bf>10 we cannot distinguish Mg and water by electron density peak profile? Even if oxygen in water has twice as much bigger radius than Mg2+?
>
> Yup. Pretty much.
>
> An "Mg+2" with B=10 is almost exactly the same density profile as a
> single point electron (atom type "Ano") with occ=9.72 and B=12.7. You
> can also fit "water" (an "O" with two "H" atoms on top of it) to Mg+2,
> and get a pretty good fit with occ=1 and B=15 for the "water". If you
> want to play around with this, I have placed a gnuplot-ish version of
> ${CLIBD}/atomsf.lib at:
>
> http://bl831.als.lbl.gov/~jamesh/pickup/all_atomff.gnuplot
>
> in gnuplot you can type:
> load 'all_atomff.gnuplot'
> plot Mg_plus_2_ff(x,20), O_ff(x,15)+2*H_ff(x,15)
>
> and stuff like that.
>
> -James Holton
> MAD Scientist
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