# How to define a new solvent in Gaussian09 to run SCRF?

I want to run computation of my system in sulphuric acid with Gaussian 09; however sulphuric acid is not among the built-in solvents in G09. I know I have to give some parameters for the new solvent I define (including static and dynamic dielectric constants). Here's an example of my input files where I try to redefine a solvent water2.

#p b3lyp/6-31G(2df,p) int(grid=ultrafine)  SCRF(Solvent=Water2,Read)

Comment

0 1

...

stoichiometry=H2O1
solventname=Water2
eps=78.3553
epsinf=1.77556


G09 keeps telling me that "SCRF(Solvent=Water2,Read)" is not correct. I want to know what the correct input will be.

• try it with SCRF=(Solvent=Generic,Read), that worked for me – pH13 - Yet another Philipp Jul 31 '15 at 7:30

The correct input should be more like (replacing your Water2 with Generic)

#p b3lyp/6-31G(2df,p) int(grid=ultrafine) SCRF(Solvent=Generic,Read)

Comment

0 1
...

stoichiometry=H2O1
solventname=Water2
eps=78.3553
epsinf=1.77556


as it is stated in the Documentation under Additional Input for PCM Calculations.

Note - this only gets your calculation running. Your shown current input section might be insufficient to properly define sulphuric acid.

As Geoff noted, the Gaussian Documentary states an important fact short before showing some $\varepsilon$-values of common solvents that should be taken into account.

We list the ε values here for convenience, but be aware it is only one of many internal parameters used to define solvents. Thus, simply changing the ε value will not define a new solvent properly.

• That's probably not sufficient. As described further along in the page you link, it says " We list the $\epsilon$ values here for convenience, but be aware it is only one of many internal parameters used to define solvents. Thus, simply changing the $\epsilon$ value will not define a new solvent properly." – Geoff Hutchison Jul 31 '15 at 14:58
• Thanks! I have tested and I've found stoichiometry, static and dynamic dielectric constants are the only parameters you need to run a default SCRF calculation. If you use Solvent=formamide in the beginning and you replace the three parameters with those of water's. you will get exactly the same result with using Solvent=Water. – Chester Lin Aug 2 '15 at 16:23