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The GAMESSUK Control Window
The GAMESSUK window provides an easytouse interface to select
the options for a GAMESSUK calculation on a molecule.
Calc Menu
Save...
Run
Write Inputfile
Write a GAMESSUK input file in the directory specified in
the Working Directory tool in the job tab. If no directory is
specified, the directory from which the CCP1GUI was started is used.
The output file will be saved with same name as the molecule being
edited, but with the suffix .in appended.
Run Inputfile
Close
Edit Menu
Input
View Menu
Input
Output
Results Summary
Molecule Tab
The options in this tab set up some of the most basic and general
options for the calculation.
Options Group
This group sets the basic options for the calculation.
Use Symmetry  by default, the GAMESSUK SCF, MCSCF and CI
modules are performed internally in a symmetry adapted basis
set. This involves the automatic generation of a symmetry
adapted list of functions driven from the input molecular
geometry and basis specified, and subsequent characterisation
of the molecular orbitals in terms of the generated list. The
Use Symmetery option toggles this behaviour on or off.
Basis Selector Group
The tools in this group are used to select which basis sets are
applied to each of the atoms in the molecule. The currently applied basis
set is shown in the Current Basis Assignment window.
Theory Tab
Guess Group
Any SCF calculation requires a guess to be made as to the form of
molecular orbitals or eigenvectors used as a starting point for the
iterative process. The guess menu tool can be used to select
between the three main methods offered by GAMESS.
Dumpfile  the Dumpfile method uses a set of orbitals
that have been calculated during a previous run of the
calculation and stored in the dumpfile (which is connected to
the GAMESSUK output stream ed3). The orbitals are read from the
dumpfile at the section specified by the counter tool. If an
UHF, GVB or UDFT calculation is performed, two sections will
need to be specified, one for the alpha orbitals and one for
the beta. If, for example, the calculation that created the dumpfile was a
UHF calculation, and the current one is one of RHF, GVB or
UDFT, then both a and b sections for the current calculation will
need to point at the section where the orbitals were stored by
the foregoing RHF calculation (the default for RHF
calculations being section1).
For an explanation of how to specify the
dumpfile for a calculation see the File Path Group in the Job Tab.
GETQ  this uses a set of orbitals from a
foreign dumpfile. A foreign dumpfile is the dumpfile
from a calculation where, for example, the geometry of the
molecule may be different to the current run, the symmetry
adapted option was different or a smaller basis set was
used. In fact the only similarities required to use a dumpfile
from a previous calcualtion using the GETQ option, is that the
ordering of the nuclei presented in the zmatrix definition
lines be the same for both. If the GETQ option is selected,
the block and section of the dumpfile where the orbtials were
written to needs to be specified:
For an explanation of how to specify the foreign dumpfile for a
calculation see the File Path Group in the Job Tab.
SCF Options
The group of options here determine the base SCF calculation
options as follows:
SCF Method This determines
the type of SCF calculation that will be undertaken. The available
options are:
RHF  a Restricted
HartreeFock calculation (closed shell).
UHF  an Unrestricted
HartreeFock calculation (open shell).
 GVB  a Generalised
Valence Bond calculation.
DFT  a Density Functional
Theory calculation (closed shell).
UDFT  an unrestricted
Density Functional Theory calculation (open shell).
Direct RHF  perform a RHF
calculation but recalculate the integrals as needed.
Direct UHF  perform a UHF
calculation but recalculate the integrals as needed.
Direct GVB  perform a GVB
calculation but recalculate the integrals as needed.
Direct DFT  perform a DFT
calculation but recalculate the integrals as needed.
Direct UDFT  perform a
UDFT calculation but recalculate the integrals as needed.
Max. Cycles  this sets the
maximum number of SCF iterations that will be carried out if the
calculation has not already converged or
run out of time by then.
Threshold  this specifies
the 'accuracy' of the calculation by determining when to stop the
SCF iterations. This occurs when the value of the
tester is equal to 10^{n}, where
n is the value specified in the threshold field (the
tester value is the largest absolute value of the
occupied/virtual block of the Fock matrix in the Molecular
Orbital basis).
Bypass SCF  if a previous
calculation has been carried out the molecule and the resulting
vectors saved in the GAMESSUK dumpfile, selecting the bypass
options causes these results to be used negating the need for a
fresh SCF calculation.
SCF Level Shifters The
tools in this group control the level shifters that can be used to
control the convergence of an SCF calculation. The level shifters
work by artificially raising the energy of the virtual
orbitals E Hartrees above the occupied orbitals,
thereby artificially stabilising the iterative process and
improving convergence. The available options are:
Initial Levelshifter Value
 the difference in energy (in Hartrees) between the virtual and
occupied orbitals for the first n cycles.
Cycle to change on  the
SCF iteration at which the levelshifter value will be altered.
Final Levelshifter Value  the energy difference
between the virtual and occupied orbitals until the
DIIS solver is in operation.
Post SCF Options
This is used to select amongst the postSCF calculations available
within GAMESSUK. The options are:
MCSCF  multiconfiguration
SCF.
MP2  secondorder
MøllerPlesset perturbation.
MP3  thirdorder
MøllerPlesset perturbation.
CCSD  coupledcluster
single and double substitution.
CCSD(T)  coupledcluster
single, double and a quasiperturbative
estimate for connected triple excitations.
Direct CI  direct
configuration interaction.
MRDCI  multireference
single and doubleexcitation configuration interaction.
Direct MP2  as standard MP2 but recalculate the
integrals as needed, as opposed to keeping them in memory
Density Functional Theory Tab
If one of the DFT options was selected in the SCF options in the
Theory tab, then the DFT options here will apply.
Functional
The functional tool is used to select the ExchangeCorrelation
Functional to be used. Available functionals are:
SVWN  Slater, Vosko, Wilk,
Nusair functional.
BLYP  Becke's
gradientcorrected exchange functional with the LeeYangParr
gradientcorrected correlation functional.
B3LYP  Becke 3parameter
hybrid exchange combined with the LYP exchangecorrelation
functional.
B97  Becke97 functional.
HCTH 
HamprechtCohenTozerHandy pure DFT functional.
FT97  Filatov and Thiel functional.
Accuracy
Together, these settings determine the accuracy of the DFT
calculation:
Grid setting  this
determines the accuracy of the Quadrature Grid.
low  should only be used
for preliminary studies; the grid is designed to obtain the total
number of electrons from the density integration with a relative
error of 1.0e4 per atom.
medium  this grid is
designed to obtain a relative error of less than 1.0e6 in the
number of electrons per atom.
high  the grid is
designed to obtain a relative error of less than 1.0e8 in the
number of electrons per atom.
very high  this grid is
significantly more accurate then the high grid, and is only
designed to be used for benchmarking calculations.
DFT Weighting Scheme  this
selects a weighting scheme to combine the atomic integration grids
to a molecular integration grid. Available schemes are:
Becke  the original Becke
weighting scheme.
MHL  the Murray, Handy
and Laming weighting scheme. This leads to more accurate integrals
than the Becke scheme.
SSF  the Stratmann,
Scuseria and Frisch weighting scheme, which seems to be the most
accurate for large quadrature grids.
MHL4SSF  the Stratmann,
Scuseria and Frisch weighting scheme with screening, but employing
the cell function by Murray, Handy and Laming weighting scheme with
μ equal to 4.
MHL8SSF  as above but with μ equal to 8.
Quadrature Types
The settings here allow the type of angular and radial integration
grid to be specified explicitly.
Coulomb Fitting
Coulomb fitting reduces the cost associated with DFT calculations
of medium sized molecules by avoiding the calculation of 4center
2electron integrals. This can be achieved by choosing a functional
without HartreeFock exchange and evaluating the Coulomb energy with
an auxiliary basis set. The tools in this group control Coulomb
Fitting.
Use Coulomb Fitting  if
this box is selected, Coulomb fitting is turned on and two
additional tools are displayed that allow the fitting to be
configured:
Schwarz Cutoff  the number
of 3centre integrals can be reduced by neglecting
those that are small enough to be considered insignificant. The
Schwarz inequality is used to decide the
cutoff point below which integrals are not important, with the
Schwarz tolerance being set to 10^{n},
where n is the number entered in the box.
Properties Tab
The options here define the molecular properties to be calculated
by GAMESSUK. The upper half of the tab is used to control the
graphical options that are to be plotted. The magnitudes of
these particular molecular properties are mapped to a grid, the
properties of which can be specified with the Edit Grid option. The molecular properties
that can be calculated are:
Difference Density  this
calculates the difference between the total electron density
associated with a molecule and the sum of the electron densities of
the atoms which constitute the molecule, but which are assumed to
have undergone no interactions with each other, and have remained
undistorted as in the free state. As such, it provides an indication
of the overall rearrangement of density which occurs when the atoms
come together upon molecular formation.
Potential  the value of
the electrostatic potential created by the electronic distribution
and nuclear charge of the molecule.
HOMO/LUMO  the Highest
Occupied Molecular Orbital and the Lowest Unoccupied Molecular
Orbital.
HOMOn/LUMOn  the
n^{th} orbital in energy below the HOMO and the
n^{th} orbital above the LUMO.
Charge Density  the
electron density associated with the molecule.
Difference Density  this
calculates the difference between the total electron density
associated with a molecule and the sum of the electron densities of
the atoms which constitute the molecule, but which are assumed to
have undergone no interactions with each other, and have remained
undistorted as in the free state. As such, it provides an indication
of the overall rearrangement of density which occurs when the atoms
come together upon molecular formation.
Potential  the value of
the electrostatic potential created by the electronic distribution
and nuclear charge of the molecule.
The options in lower half of the tab determine that GAMESSUK
should calculate the force constants that determine the
vibrational frequencies of the molecule. This can be done in
two ways namely:
Finite Difference  this indicates that
GAMESSUK will calculate the force constants numerically
by taking finite differences of the gradient using a onepoint
formula.
Analytic  this option is a combination of
tasks, requesting integral generation, SCF, gradient
evaluation (with additional evaluation of derivative Fock
operators), integral transformation, solution of the coupled
HartreeFock (CHF) equations, calculation of the twoelectron
second derivative contribution and, finally, determination of
the projected harmonic frequencies. This approach is generally
more accurate than the numerical approach, but is only
vialable for SCF and DFT wavefunctions, together
with MP2 closedshell wavefunctions.
NB: the above options are only applicable if
the geometry of the molecule has already been optimised in a
previous calculation or if an optimisation is carried out as
part of the current calculation.
Edit Grid
When a graphical analysis option is selected, the GAMESSUK
calculation will output a grid of points where the selected molecular
property has been calculated at each point. The Edit Grid
button brings up a separate window which
can be used to tune the properties of the Grid. The options available
for the grid are:
X,Y,Z Tran  the slider can be
used to shift the origin of the grid's x,y, or
zaxis. Alternatively the shift can be specified in Angstroms
and entered in the box to the right of the slider.
X,Y,Z Rot  the slider can be used to rotate the
grid about the x,y or zaxis. Alternatively the angle of
rotation can be entered in the box to the right of the
slider.
X,Y,Z Scale  the slider can be used to scale
the length of the x,y or zaxis, or the relative
value can be entered in the box to the right.
nx, ny, nz  this counter is used
to specify the 'mesh density' along the x,y or zaxis. For rectangular
grids, this is the total number of points along the axis.
Transform  apply any
changes that are pending.
Close and Save  close the
Grid Editor window and return to the calculation window, saving any
changes that have been made.
Reset  reset the grid to
its default values.
Close and Cancel  close the Grid Editor window and
return to the calculation window, but discard any changes that have
been made.
Optimisation Tab
If the Task has been selected as Geometry Optimisation
in the Molecule Tab, then the options here determine how the
geometry optimisation will proceed.
Runtype Group
The options in this group determine the type of geometry
optimisation that will be carried out.
Locate Transition State  if this checkbox is selected
then the geometry optimisation will not
search for the global minimum, but will instead try and determine
the geometry of a transition state. A transition state search can
only be undertaken if the zmatrix is in internal coordinate form
and the variables that are to be optimised have been specified.
Search Procedure Group
The options in this group allow the user a certain amount
of control over the implementation of the selected optimisation
strategy.
Convergence Thresh.  this determines the convergence
threshold: the point at which the geometry
optimisation is deemed to have converged.
For a Zmatrix minimisation or Transition State Search, this is
when:
maximum change in variables <
Convergence Threshold
average change in variables <
Convergence Threshold * 2/3
maximum gradient <
Convergence Threshold * 4/9
average gradient < Convergence Threshold * 8/27
For a Cartesian optimisation, this is when:
Max. Step Size  this determines the largest change
that will be permitted to be made to variables during the
optimisation. If a ZMatrix minimisation or
Transition State Search is being carried out this this number
determines the maximum change in bond length in Bohrs, or change in
bond angle in radians. For a Cartesian
optimisation the number specifies the maximum permitted change in
the Cartesian coordinates.
Jorgensen Group
If the checkbox is selected it indicates that the Jorgensen/Simmons
quasiNewtonRaphson minimisation algorithm should be used. This is
only applicable when a ZMatrix minimisation or Transition
State Search is being undertaken.
Hessian Update Procedure  this option is only
displayed if the geometry optimisation is searching for a minimum
and not a transition state. If displayed it can be used to select
whether the Hessian update procedure is the default, BFGS, or BFGSX
(a modified BFGS update procedure with safeguards to ensure
retention of a positive definite Hessian).
Job Tab
The tools in this tab set up various external atrributes of the
GAMESSUK that will be run.
Job Group
The tools in this group are used to configure the environment that
the GAMESSUK job will be run in.
File Path Group
The tools in this tab set the names and locations of the files that
will be connected to the various ed streams used by GAMESSUK.
ECP Libraries  ed0 is used to specify the
directory containing the pseudopotential libraries used for nonlocal
pseudopotential calculations. If the specify button is
clicked, a text window and browse button will appear, which
can be used to specify the location of this directory.
Mainfile (ed2)  this file is used to hold the
two electron integrals generated by GAMESSUK. If the
keep button is selected, this file will be saved in the
directory the calculation is run in, with the name specified by
the jobname tool and the suffix .ed2. If the
specify button is selected, the name and location can
be specifed as desired.
Dumpfile (ed3)  the dumpfile holds a variety of
information including the eigenvectors, restart information
Hessians, CIcoefficients etc. You must save the dumpfile for
a calculation if you intend to undertake any subsequent
calculations based on the results of this calculation. It is
also vital to specify the dumpfile you wish to use if you are
performing a calculation that requires any information
contained in the dumpfile from a previous calculation. It is important to
note that the dumpfile from a previous calculation will be
overwritten with the new values if it is specifed here.
If this is the first of a series of calculations and no
information from previous calculations is requried, the
keep button will cause the dumpfile for this
calculation to be saved in the directory the calculation is
running in, with the name specified by
the jobname tool and the suffix
.ed3. Alternatively, the specify button can
be used to select an arbitrary name and location. If the
current calculation uses information from a previous
calculation, then the same applies, but the eigenvector
information will be read from this file, before
the values are overwritten with those for the current calculation.
Tempfile (ed7)  this file is the temporary file
used by GAMESSUK and holds various housekeeping information
used by the program as it runs. Normally this file is located
in the directory specified by the GAMESS_TMP environment
variable, or, failing that, the directory specified by the GAMESS_SCR enviroment
variable, or, as a last resort, the directory that the
calculation runs in. If for any reason you believe there may
not be enough space in any of these directories, or they are
located on disks that are not fast enough, an alternative
location can be specifed with this tool. If the
keep button is selected, this file will be saved in the
directory the calculation is run in, with the name specified by
the jobname tool and the suffix .ed7. If the
specify button is selected, the name and location can
be specifed as desired.
Foreign Dumpfile (ed14)  this is used to
specify the location of a foreign dumpfile. For more
information about foreign dumpfiles see the GETQ option
in the Guess Section of the Theory
Tab. It is important to note that if a file is specified
as a foreign dumpfile, it is only read from and not
written to. If the dumpfile for the current calculation is to
be kept, it should be specified with the ed3 dumpfile tool
described above.
If the specify button is clicked, a text window and browse button will appear, which
can be used to specify the location of this file.
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