Running SCRF Calculations

The SCRf keyword in the route section of a Gaussian job requests a calcuJation in the presence of a solvent. SCRF calculations generally require an additional input line following the molecule specification section s terminating blank line, having the following form  

Remember that e is the dielectric constant of the solvent. The examples show the value for cyclohexane (2.0). 

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An SCRF frequency calculation at the two SCRF optimized structures. Note that frequency calculations must be run as a separate job step for SCRF calculations (Opt Freq does not do what might be expected). 

Compute the frequency associated with carbonyl stretch in solution with acetonitrUe for the carbonyl systems we looked at in the gas phase in Chapter 4. Run your calculations using RHF/6-31+G(d) with the Onsager SCRF model. Discuss the substituent effect on the predicted solvent effects. 

Gaussian also includes a fecility for estimating molecular volumes for SCRF ipole calculations. An energy calculation run with the Vi unw keyword will produce an estimate value for Oq. For example, here is the output indicating the recommended value for oq (or formaldehyde (RHF/6-31+G ) ... 

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