CCL: PCM and dipole moment

Gonzalo,

PCM uses the complete density evaluated from the wave function. As such, it is equivalent to a multipole expansion carried to infinite order (although in practice one rarely needs to go beyond about l = 12 for a moderately sized molecule before multipole expansions and PCM agree to within the noise in the respective methods -- lower still when distributed multipoles are used instead of a single-center expansion).

For a complete discussion of this and some other points comparing continuum models, see

Curutchet, C.; Cramer, C. J.; Truhlar, D. G.; Ruiz Lopez, M.; Orozco, M.; Luque, F. J. "Electrostatic Component of Solvation: Comparison of SCRF Continuum Models" J. Comput. Chem. 2003, 24, 284.

Chris

On Mar 7, 2006, at 9:13 PM, Gonzalo Jimenez Oses gonzalo.jimenez*dq.unirioja.es wrote:

Sent to CCL by: "Gonzalo Jimenez Oses" [gonzalo.jimenez{:}dq.unirioja.es]
Dear CCL'ers:

I wonder if there is any short way to stablish a coherent relationship between the free solvation energy (or, at least, the electrostatic part) obtained through a PCM method (IEF-PCM, C-PCM, D-PCM) and the dipole (or any other multipole) moment of a molecule.
I have read that solvation models based on a multipole moment expansion (MPE) of the solute charge distribution, like the Onsagers original model, solvation is described explicitly in terms of a dipole moment.
However, solvation models based in an apparent surface charge (ASC) like PCM seem not to take the multipole moments into consideration in a explicit way.

Could anyone shed some light into this question, please?

Thank you very much in advance,

Gonzalo



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Christopher J. Cramer

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