# CCL:G: PCM and TD-DFT

*From*: "Tom de Greef" <t.f.a.d.greef],[tue.nl>
*Subject*: CCL:G: PCM and TD-DFT
*Date*: Mon, 17 Dec 2007 04:28:20 -0500

Sent to CCL by: "Tom de Greef" [t.f.a.d.greef|*|tue.nl]
Dear all,
I have a question about the use of TD-DFT calculations including PCM solvent
effects using Gaussian 03. I have read in several papers that the best method to
use the PCM solvent model in combination with TD-DFT is the non-equilibrium
approach (when one is interested in the fast absorption processes). The solvent
reaction field in the non-equilibrium regime depends in the PCM formalism on the
dielectric constant at optical frequency (for CHCl3 this is 1.2). The default
TD-DFT calculations in Gaussian03 assumes a non-equilibrium approach
(NonEquilSolv is default). However, when I start a TD-DFT calculation in
Gaussian03 for CHCl3 it automatically takes the value of the dielectric constant
(for CHCl3 this is 4.9) for the calculation. Does this mean that I need to
define the dielectric constant in an explicit way (by addition of the keyword:
EPS=1.2)???
With best regards,
Tom