$CONTRL group (optional)

This is a free format group specifying global switches.

    SCFTYP together with MPLEVL specifies the wavefunction.  
           You may choose from:

           = RHF       Restricted Hartree Fock calculation
                       (default for EVEN number of electrons)
           = UHF       Unrestricted Hartree Fock calculation
                       (default for ODD number of electrons)
           = ROHF      Restricted open shell Hartree-Fock.
                       (high spin, see GVB for low spin)
           = GVB       Generalized valence bond wavefunction
                       or OCBSE type ROHF. (needs $SCF input)
           = MCSCF     Multiconfigurational SCF wavefunction
                       (this requires $DRT input)
           = CI        Configuration Interaction calculation
                       (this requires $DRT input)

    MPLEVL = n         chooses Moller-Plesset perturbation level.  
                       The default is 0 to skip. This is implemented only 
                       for n=2, only for RHF, UHF, and ROHF wave functions, 
                       and only for ENERGY, TRUDGE,SURFACE, and FFIELD run
                       types.

    RUNTYP specifies the type of computation, for example at a single geometry point:

           = ENERGY    Single point energy. (default)
           = GRADIENT  Single point energy plus gradient.
           = HESSIAN   Compute energy second derivatives, and
                       perform harmonic vibrational analysis.
                       See the $FORCE group.

           multiple geometry options:

           = OPTIMIZE  Optimize the molecular geometry using
                       analytic energy gradients. See $STATPT.
           = TRUDGE    Non-gradient total energy minimization.
                       See groups $TRUDGE and $TRURST.
           = SADPOINT  Locate saddle point (transition state).
                       See the $STATPT group.
           = IRC       Follow intrinsic reaction coordinate.
                       See the $IRC group.
           = GRADEXTR  Trace gradient extremal. See the $GRADEX group.
           = DRC       Follow dynamic reaction coordinate. See the $DRC group.
           = SURFACE   Scan linear cross sections of the potential energy surface.
                       See $SURF.

           single geometry property options:

           = PROP      Properties will be calculated.  A $DATA
                       deck and converged $VEC group should be
                       input.  Optionally, Boys localization
                       can be done.  See $ELPOT, etc.
           = MOROKUMA  Performs dimer energy decomposition. See the $MOROKM
                       group.
           = TRANSITN  Find radiative transition moment.
                       See the $TRANST group.
           = SPINORBT  Find spin-orbit coupling constant.
                       See the $TRANST group.
           = FFIELD    applies finite electric fields, most
                       commonly to extract polarizabilities.
                       See the $FFCALC group.
           = TDHF      analytic computation of time dependent polarizabilities.
                       See the $TDHF group.

Note that RUNTYPs involving the energy gradient (GRADIENT, HESSIAN, OPTIMIZE, SADPOINT, and IRC) cannot be used with SCFTYP=CI, or nonzero MPLEVL.
    EXETYP = RUN       Actually do the run. (default)
           = CHECK     Wavefunction and energy will not be
                       evaluated.  This lets you speedily
                       check input and memory requirements.
                       See the overview section for details.
           = DEBUG     Massive amounts of output are printed,
                       useful only if you hate trees.
           = routine   Maximum output is generated by the
                       routine named.  Check the source for
                       the routines this applies to.

    MAXIT  =           Maximum number of SCF iteration cycles.
                       Pertains only to RHF, UHF, ROHF, or
                       GVB runs.  See also MAXIT in $MCSCF.
                       (default = 30)


    ICHARG =           Molecular charge.  (default=0, neutral)

    MULT   =           Multiplicity of the electronic state
           = 1         singlet (default)
           = 2,3,...   doublet, triplet, and so on.

ICHARG and MULT are used directly for RHF, UHF, ROHF. For GVB, these are implicit in the $SCF input, while for MCSCF or CI, these are implicit in the $DRT input. However, you must still give them correctly here.
    ECP    =           effective core potential control.
           = NONE      all electron calculation (default).
           = READ      read the potentials in $ECP group.
           = SBK       use Stevens, Basch, Krauss, Jasien,
                       Cundari potentials for all heavy 
                       atoms (Li-Rn are available).
           = HW        use Hay, Wadt potentials for all the
                       heavy atoms (Na-Xe are available).

The next three control molecular geometry

    COORD  =           choice for molecular geometry in $DATA.
           = UNIQUE    only the symmetry unique atoms will be
                       given, in Cartesian coords (default).
           = HINT      only the symmetry unique atoms will be
                       given, in Hilderbrandt style internals.
           = CART      Cartesian coordinates will be input.
           = ZMT       GAUSSIAN style internals will be input.
           = ZMTMPC    MOPAC style internals will be input.

Note that the final three choices require the input of all atoms in the molecule. GAMESS will orient the molecule, and determine which atoms are unique. The reorientation is likely to change the order of the atoms from what you input.
Note that the final three choices require the use of $BASIS to define the basis set. The first two choices may or may not use $BASIS, as you wish.
    UNITS  =           distance units, any angles which are
                       entered in $DATA must be in degrees.
           = ANGS      Angstroms (default)
           = BOHR      Bohr atomic units

    NZVAR  =           Coordinate switch.
           = 0         Use Cartesian coordinates (default).
           = M         If COORD=ZMT or ZMTMPC and a $ZMAT is
                       not given:  the internal coordinates
                       will be those defining the molecule in
                       $DATA.  In this case, $DATA must not
                       contain any dummy atoms.  M is usually
                       3N-6 (or 3N-5 for linear).
           = M         For other COORD choices, or if $ZMAT is
                       given:  the internal coordinates will
                       be those defined in $ZMAT.  This allows
                       the use of more sophisticated internal
                       coordinate choices.  M is ordinarily
                       3N-6 (3N-5), unless linear bends are
                       used in the $ZMAT.

Note that NZVAR refers mainly to the coordinates in which an OPTIMIZE or SADPOINT run is performed, but also to the values printed for any of the other run types. It is possible to use internals to enter the molecule, but still to use Cartesians during the optimization!
    LOCAL  =           controls orbital localization.
           = NONE      Skip localization (default).
           = BOYS      Do Foster-Boys localization.
           = RUEDNBRG  Do Edmiston-Ruedenberg localization.
           = POP       Do Pipek-Mezey population localization.
                       See the $LOCAL group.   Localization
                       does not work for SCFTYP's GVB or CI.

Interfaces to other programs

    MOLPLT = flag that produces an input deck for a molecule
             drawing program distributed with GAMESS.
             (default is .FALSE.)

    PLTORB = flag that produces an input deck for an orbital
             plotting program distributed with GAMESS.
             (default is .FALSE.)

    AIMPAC = flag to create an input deck for Bader's atoms
             in molecules properties code. (default=.FALSE.) 
             For information about this program, contact 
                 Richard F.W. Bader
                 Dept. of Chemistry
                 McMaster University
                 Hamilton, Ontario  L8S-4M1 Canada
                 bader@sscvax.cis.mcmaster.ca

    RPAC   = flag to create the input files for Bouman and
             Hansen's RPAC electronic excitation and NMR
             shieldings program.  RPAC works only with
             RHF wavefunctions.  Contact Prof. Aage Hansen
             in Copenhagen (nahaeh@vm.uni-c.dk) about this 
             program.  (default is .FALSE.)

    FRIEND = string to prepare input to other quantum
             programs, choose from
           = HONDO    for HONDO 8.2
           = MELDF    for MELDF
           = GAMESSUK for GAMESS (UK Daresbury version)
           = GAUSSIAN for Gaussian 9x
           = ALL      for all of the above

PLTORB, MOLPLT, and AIMPAC decks are written to file PUNCH at the end of the job. The two binary disk files output by RPAC are written at the end of the job. Thus all of these correspond to the final geometry encountered during the job.

In contrast, selecting FRIEND turns the job into a CHECK run only, no matter how you set EXETYP. Thus the geometry is that encountered in $DATA. The input is added to the PUNCH file, and may require some (usually minimal) massaging.

PLTORB and MOLPLT are written even for EXETYP=CHECK. AIMPAC requires at least RUNTYP=PROP. RPAC requires at least RUNTYP=ENERGY, and you must take action to save the binary files AOINTS and WORK15.

The NBO program of Frank Weinhold's group can be attached to GAMESS. The input to control the natural bond order analysis is read by the add in code, so is not described here. The NBO program is available by anonymous FTP to ftp.osc.edu, in the directory /pub/chemistry/software/SOURCES/FORTRAN/nbo

Computation control switches

For the most part, the default is the only sensible value, and unless you are sure of what you are doing, these probably should not be touched.

    NPRINT =           Print/punch control flag
                       See also EXETYP for debug info.
                       (options -7 to 5 are primarily debug)
           = -7        Extra printing from Boys localization.
           = -6        debug for geometry searches
           = -5        minimal output
           = -4        print 2e-contribution to gradient.
           = -3        print 1e-contribution to gradient.
           = -2        normal printing, no punch file
           =  1        extra printing for basis,symmetry,ZMAT
           =  2        extra printing for MO guess routines
           =  3        print out property and 1e- integrals
           =  4        print out 2e- integrals
           =  5        print out SCF data for each cycle.
                       (Fock and density matrices, current MOs
           =  6        same as 7, but narrow terminal output
                       This option isn't perfect.
           =  7        normal printing and punching (default)
           =  8        more printout than 7. The extra output
                       is (AO) Mulliken and overlap population
                       analysis, eigenvalues, Lagrangians, ...
           =  9        everything in 8 plus Lowdin population
                       analysis, final density matrix.

Restart options

    IREST  =       restart control options
                   (for OPTIMIZE run restarts, see $STATPT)
                   Note that this option is unreliable!
           = -1    reuse dictionary file from previous run,
                   useful with GEOM=DAF and/or GUESS=MOSAVED.
                   Otherwise, this option is the same as 0.
           = 0     normal run (default)
           = 1     2e restart (1-e integrals and MOs saved)
           = 2     SCF restart (1-,2-e integrls and MOs saved)
           = 3     1e gradient restart
           = 4     2e gradient restart

    GEOM   =       select where to obtain molecular geometry
           = INPUT from $DATA input (default for IREST=0)
           = DAF   read from DICTNRY file (default otherwise)

As noted in the first chapter, binary file restart is not a well tested option!

    NOSYM  = 0     the symmetry specified in $DATA is used
                   as much as possible in integrals, SCF,
                   gradients, etc.  (this is the default)
           = 1     the symmetry specified in the $DATA group
                   is used to build the molecule, then
                   symmetry is not used again.   Some GVB
                   or MCSCF runs (those without a totally
                   symmetric charge density) require you
                   request no symmetry.

    INTTYP = POPLE use fast Pople routines for sp integral
                   blocks, and HONDO Rys polynomial code for
                   all other integrals.  (default)
           = HONDO use HONDO/Rys integrals for all integrals.
                   This option produces slightly more accurate
                   integrals but is also slower.

    NORMF  = 0     normalize the basis functions (default)
           = 1     no normalization

    NORMP  = 0     input contraction coefficients refer to
                   normalized Gaussian primitives. (default)
           = 1     the opposite.

    ITOL   =       primitive cutoff factor (default=20)
           = n     products of primitives whose preexponential
                   factor is less than 10**(-n) are skipped.

    ICUT   = n     integrals less than 10.0**(-n) are not
                   saved on disk. (default = 9)