Suggested GAMESS Keywords for "Large" Molecules (> 15 atoms)

Gas Phase Single point energy (RHF)

 $CONTRL RUNTYP=ENERGY $END
 $SYSTEM TIMLIM=99999999999 MWORDS=5 $END
 $SCF DIRSCF=.T. FDIFF=.T. NPUNCH=0 $END

Aqueous Phase Single point energy (RHF)

 $CONTRL RUNTYP=ENERGY $END
 $SYSTEM TIMLIM=99999999999 MWORDS=5 $END
 $SCF DIRSCF=.T. FDIFF=.T. NPUNCH=0 $END
 $PCM IEF=-3 ICOMP=2 SOLVNT=WATER RET=100 $END
 $TESCAV NTSALL=240 $END

Gas Phase Geometry Optimization (RHF) (n=number of atoms)

 $CONTRL RUNTYP=OPTIMIZE NZVAR=(3n-6) $END
 $SYSTEM TIMLIM=99999999999 MWORDS=5 $END
 $SCF DIRSCF=.T. FDIFF=.T. NPUNCH=0 $END
 $ZMAT DLC=.T. AUTO=.T. $END
 $STATPT NSTEP=50 OPTTOL=0.0005 NPRT=-2 NPUN=-2 $END

Aqueous Phase Geometry Optimization (RHF) (n=number of atoms)

 $CONTRL RUNTYP=OPTIMIZE NZVAR=(3n-6) $END
 $SYSTEM TIMLIM=99999999999 MWORDS=5 $END
 $SCF DIRSCF=.T. FDIFF=.T. NPUNCH=0 $END
 $ZMAT DLC=.T. AUTO=.T. $END
 $STATPT NSTEP=100 OPTTOL=0.0002 NPRT=-2 NPUN=-2 $END
 $PCM IEF=-10 SOLVNT=WATER RET=100 $END
 $TESCAV MTHALL=2 $END

Other Common Input Options

Wavefunction, Charge and Multiplicity (Defaults)

 $CONTRL SCFTYP=RHF ICHARG=0 MULT=1 $END

Density Functional Calculations

 $DFT DFTTYP=B3LYP $END

MP2 Calculations (XX = large as possible)

 $CONTRL MPLEVL=2 $END 
 $SYSTEM TIMLIM=99999999999 MWORDS=XX $END  

Popular Basis Sets

6-31+G(2d,p)

 $BASIS GBASIS=N31 NGAUSS=6 NDFUNC=2 NPFUNC=1 DIFFSP=.T. $END

6-31G(d) = 6-31G*

 $BASIS GBASIS=N31 NGAUSS=6 NDFUNC=1 $END

3-21G

 $BASIS GBASIS=N21 NGAUSS=3 $END

STO-3G

 $BASIS GBASIS=STO NGAUSS=3 $END

AM1

 $BASIS GBASIS=AM1 $END

Stevens-Basch-Krauss-Jasien-Cundari Effective Core Potential (H - Rn)

 $CONTRL ECP=SBKJC $END
 $BASIS GBASIS=SBKJC NDFUNC=1 $END