Dear
Antarip,
You are right, dipole moment for
charged systems is an ill-defined quantity as it is gauge-dependent. If your
molecules are different i.e. number or arrangement of atoms are
different it is better to forget about any direct comparison! I suggest
that you add counter ions and measure the dipole moment in the presence of those
counter ions. Nevertheless, counter ions almost always accompany a charged
system. If you are really interested to measure the dipole moment
for your systems without counter ions then I suggest to first add some counter
ions, then optimize your molecules in the presence of them and prepare
wavefunction (WFN) files. You can analyze the WFNs by QTAIM and separate the
atomic moment of the counter ions from the total moment. The remaining moment is
dipole of your charged system. Now, it is not gauge dependent!
Good luck,
Cina
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Cina Foroutan-Nejad, Ph.D.
From: "Antarip Halder
antarip.halder,gmail.com" <owner-chemistry{:}ccl.net>
To: "Foroutan-Nejad, Cina "
<canyslopus{:}yahoo.co.uk>
Sent: Tuesday, 7 May 2013, 7:50
Subject: CCL:G: Dipole moment of charged
species in Gaussian
Dear All,
I am trying to
calculate the dipole moment of charged species using Gaussian and I have to
compare dipole moments of different singly charged species. I am aware of the
fact that dipole moment for the molecular species which have non zero charge is not
defined. The comparison can be performed only in the case when the position of
coordinate origin is not changed.
Can any one tell me how can I define the origin to calculate
the dipole moment.
Thanks in advance.
Antarip Halder
MS by Research
Center for Computational Natural Sciences and
Bioinformatics
International Institute of Information Technology,
Hyderabad
Andhra Pradesh, India
--
If you think you can, you
are right.
--
If you think you can, you are
right.