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
