Dear Niladri,
The first column is the number of the atom. The second is the number of
electrons. So in your case: the oxygens are atom 1 and 4 (this is the number in
your input), the rest are hydrogens. For example atom 1 has 5.728 electrons.
Neutral oxygen has 6 valence electrons (the 1s electrons are in the core and
therefore simulated by the pseudopotential), so the charge of this atom is
6-5.728 = 0.272
Atoms 2 and 3 are charged -0.137 and -0.135 respectively.
That the oxygens are positive and the hydrogens negative already confirms that
Mulliken charges are not reliable. For force field calculations, people tend to
use ESP charges. I don't know if these can be calculated from SIESTA output. I
am cc'ing this to the list, but I doubt if it's built in at the moment.
Hope this helps,
Herbert
niladri patra wrote:
HI ,,
Here is the part of teh output file...
mulliken: Atomic and Orbital Populations:
Species: H
Atom Qatom Qorb
1s 1s 1Ppy 1Ppz 1Ppx
2 1.137 0.390 0.498 0.061 0.099 0.089
3 1.135 0.392 0.495 0.033 0.110 0.106
5 1.135 0.397 0.486 0.081 0.081 0.088
6 1.132 0.398 0.483 0.061 0.077 0.111
Species: O
Atom Qatom Qorb
2s 2s 2py 2pz 2px 2py 2pz 2px
2Pdxy 2Pdyz 2Pdz2 2Pdxz 2Pdx2-y2
1 5.728 0.748 0.616 0.796 1.451 1.379 0.397 0.145 0.170
0.003 0.004 0.003 0.008 0.007
4 5.734 0.762 0.608 1.118 1.297 1.233 0.278 0.217 0.199
0.006 0.003 0.002 0.006 0.007
mulliken: Qtot = 16.000
So what would be the charge of atom 1 , 2 and 3 (individually)? Actually
I need the partial atomic charge , so that I can put this charge into
other MD calculation.
THanks,
Niladri
--
Herbert Fruchtl
Senior Scientific Computing Officer
School of Chemistry, School of Mathematics and Statistics
University of St Andrews
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The University of St Andrews is a charity registered in Scotland:
No SC013532
