[spirochete]

I'm trying to use Guassian 09 to calculate Delta G Solvation.  So far I can only get it to calculate SCF in solution.  I want it to calculate SCF Gas phase in the same output file:


#b3lyp/6-31+g(d,p) scf=(maxcycle=300,direct,tight) density=current
SCRF=(PCM,SOLVENT=DiChloroEthane,SMD,DoVacuum)

What is missing here to automatically do a Gas phase SCF calculation in the same output file?  SCFVAC under "Read" used to do this in Gaussian 03.  The input file above still is giving me solution SCF only.  Thanks in advance.

[Jammyzx]

Hi,
   Have been trying to do a similar calculation, from what I have read I don't think it is possible. Seems the only way is to run the solution phase calculation and the gas phase calculation and take the difference in the energies to be the delta G solvation. 

[tamim83]

I don't see anything wrong with your input.  SCRF=DoVacuum should do the trick according to the G09 manual.  Are you sure the Gas phase SCF energy isn't embedded in the output file someplace?

[xir]

i would remove this line to for a normal gas phase calculation "SCRF=(PCM,SOLVENT=DiChloroEthane,SMD,DoVacuum)"

[Jammyzx]

Hi,
         SCRF=(PCM,SOLVENT=DiChloroEthane,SMD,DoVacuum) This input seems to be specifying two solvation models, PCM tells G09 to use IEFPCM and SMD tells G09 to use the SMD model. I don't know if that affects your calculation at all but if you are planning to use SMD then this input should work fine:

SCRF=(SMD,SOLVENT=DiChloroEthane,DoVacuum)

The G09 SCRF manual page states the following to calculate the delta G of solvation:

"Do an IEFPCM calculation with radii and non-electrostatic terms for Truhlar and coworkers’ SMD solvation model [Marenich09]. This is the recommended choice for computing ΔG of solvation, which accomplished by performing gas phase and SCRF=SMD calculations for the system of interest and taking the difference the resulting energies."

at the following link http://www.gaussian.com/g_tech/g_ur/k_scrf.htm

I don't believe you can get all of the information in one output as the manual suggests you need to run both gas phase an solution phase calculations and take the difference in the energies to be delta G of solvation at a 1mol/L standard state.

hope that helps.