Eric Shamay wrote:
In researching the shell model used to create "polarizable" ions I came
across several of the references of the drude oscillator approach and
the papers of van der Spoel (for the SW water model) and Roux (for the
parameters of the halides and alkalis). However, perhaps due to my own
oversight, I did not walk away from those publications having a firm
understanding of just how one goes about developing the parameters
necessary to implement the shell model, even for simple monovalent ions
(i.e. sodium).
I am attempting to simulate an aqueous sodium chloride system using a
polarizable (shell) model for the individual sodium and chloride ions,
but eventually I will also need data for nitrate and sulfate ions. Is
there a more clear reference that illustrates the process (or lists the
results) of developing the parameters (force constant [k], charge of the
shell particle [q_s], etc.) for using the shell model? I'd like to be
able to come up with my own values, but a published set will work as
well. As a side note, I'm coming from having used the amber
point-polarizable model that assigns an isotropic alpha to each
particle. I can calculate the polarizability tensor using DFT methods,
but still don't know how to translate that into a force constant or
shell-particle charge.
The equations are in the SW paper. However in case of a singly charged
atom like Na+ you have one extra degree of freedom. In case of molecular
ions you can use e.g. RESP calculations to get the partial charges and
use these to determine the spring constant.
Note that you will also need to update Van der Waals parameters.
thank you,
~Eric Shamay
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David van der Spoel, Ph.D., Professor of Biology
Molec. Biophys. group, Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone: +46184714205. Fax: +4618511755.
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