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$SVP group (optional)
The presence of this group in the input turns on use of
the Surface and Simulation of Volume Polarization for
Electrostatics (SS(V)PE) solvation model, or the more exact
Surface and Volume Polarization for electrostatics (SVPE)
model. These treat the solvent as a dielectric continuum,
and are available with either an isodensity or spherical
cavity around the solute. The solute may be described only
by RHF, UHF, ROHF, GVB, or MCSCF wavefunctions. The energy
is reported as a free energy, which includes the factor of
1/2 that accounts for the work of solvent polarization
assuming linear response. Gradients are not yet available.
In addition, the CMIRS (Composite Method for Implicit
Representation of Solvent) model may be invoked to combine
SS(V)PE with the DEFESR (Dispersion, Exchange, and Field-
Extremum Short-Range) model to achieve a more complete
treatment of solvation. The field-extremum contribution is
designed to describe hydrogen bonding effects.
The current version 1.0 of CMIRS has parameters for
water solvent with isodensity cavities having contours of
0.0005, 0.001, or 0.002 au for use with the B3LYP/6-31+G*,
B3LYP/G3large, HF/6-31+G*, or HF/G3large electronic
structure methods. In addition, parameters are also
available for cyclohexane and benzene solvents with
isodensity cavities having contours of 0.0005, 0.001, or
0.002 au for use with the B3LYP/6-31+G* method.
Typical use of these methods will involve a prior step
to do an equivalent calculation on the given solute in the
gas phase. This provides a set of orbitals that can be
used as a good initial guess for the subsequent run
including solvent. It also provides the gas phase energy
(input as keyword EGAS) that can be subtracted from the
energy in solvent to obtain the free energy of solvation.
Many runs will be fine with all parameters set at
their default values. The most important parameters a user
may want to consider changing are:
NVLPL = treatment of volume polarization
0 - SS(V)PE method, which simulates volume
polarization by effectively folding in an
additional surface polarization (default)
N - SVPE method, which explicitly treats volume
polarization with N extra layers
DIELST = static dielectric constant of solvent
(default = 78.39, appropriate for water)
IVERT = 0 do an equilibrium calculation (default)
1 do a nonequilibrium calculation to get the final
state of a vertical excitation - this requires
that IRDRF=1 to read the $SVPIRF input group
that was punched with IPNRF=1 in a run on the
initial state - note that a meaningful result is
obtained only if the initial and final states
both come from the same wavefunction/basis set/
geometry/solvation model.
DIELOP = optical dielectric constant of solvent -
this only relevant if IVERT=1
(default 1.776, appropriate for water)
EGAS = gas phase energy (optional): if given, the program
will output the free energy of solvation and the
change in solute internal energy due to solvation.
Note that a meaningful result is obtained only if
EGAS comes from the same wavefunction/basis set/
geometry as is used in the solvation calculation
ISHAPE = sets the shape of the cavity surface
0 - electronic isodensity surface (default)
1 - spherical surface
RHOISO = value of the electronic isodensity contour used to
specify the cavity surface, in electrons/bohr**3
(relevant if ISHAPE=0; default=0.001)
RADSPH = sphere radius used to specify the cavity surface.
A positive value means it is given in Bohr,
negative means Angstroms. (relevant if ISHAPE=1;
default is half the distance between the
outermost atoms plus 1.4 Angstroms)
INTCAV = selects the surface integration method
0 - single center Lebedev integration (default)
1 - single center spherical polar integration,
not recommended; Lebedev is far more efficient
NPTLEB = number of Lebedev-type points used for single
center surface integration. The default value
has been found adequate to obtain the energy to
within 0.1 kcal/mol for solutes the size of
monosubstituted benzenes. (relevant if INTCAV=0)
Valid choices are 6, 14, 26, 38, 50, 86, 110, 146,
170, 194, 302, 350, 434, 590, 770, 974, 1202,
1454, 1730, 2030, 2354, 2702, 3074, 3470, 3890,
4334, 4802, 5294, or 5810. (default=1202)
NPTTHE, NPTPHI = number of (theta,phi) points used for
single center surface integration. These should
be multiples of 2 and 4, respectively, to provide
symmetry sufficient for all Abelian point groups.
(relevant if INTCAV=1; defaults = 8,16; these
defaults are probably too small for all but the
tiniest and simplest of solutes.)
TOLCHG = a convergence criterion on the program variable
named CHGDIF, which is the maximum change in any
surface charge from its value in the previous
iteration (default=1.0D-6). This is checked in
each SCF iteration, although the actual value
is not printed until final convergence is reached.
The single-center surface integration approach may fail for
certain highly nonspherical molecular surfaces. The program
will automatically check for this and bomb out with a
warning message if need be. The single-center approach
succeeds only for what is called a star surface, meaning
that an observer sitting at the center has an unobstructed
view of the entire surface. Said another way, for a star
surface any ray emanating out from the center will pass
through the surface only once. Some cases of failure may be
fixed by simply moving to a new center with the ITRNGR
parameter described below. But some surfaces are inherently
nonstar surfaces and cannot be treated with this program
until more sophisticated surface integration approaches are
implemented.
ITRNGR = translation of cavity surface integration grid
0 - no translation (i.e., center the grid at the
origin of the atomic coordinates)
1 - translate to center of nuclear mass
2 - translate to center of nucl. charge (default)
3 - translate to midpoint of outermost atoms
4 - translate to midpoint of outermost
non-Hydrogen atoms
5 - translate to user-specified coordinates,
in Bohr
6 - translate to user-specified coordinates,
in Angstroms
TRANX, TRANY, TRANZ = x,y,z coordinates of translated
cavity center, relevant if ITRNGR=5 or 6.
(default = 0,0,0)
IROTGR = rotation of cavity surface integration grid
0 - no rotation
1 - rotate initial xyz axes of integration grid to
coincide with principal moments of nuclear
inertia (relevant if ITRNGR=1)
2 - rotate initial xyz axes of integration grid to
coincide with principal moments of nuclear
charge (relevant if ITRNGR=2; default)
3 - rotate initial xyz axes of integration grid
through user-specified Euler angles as defined
by Wilson, Decius, Cross
ROTTHE, ROTPHI, ROTCHI = Euler angles (theta, phi, chi) in
degrees for rotation of the cavity surface
integration grid, relevant if IROTGR=3.
(default=0,0,0)
IOPPRD = choice of the system operator form. The default
symmetric form is usually the most efficient, but
when the number of surface points N is big it can
require very large memory (to hold two N by N
matrices). The nonsymmetric form requires solution
of two consecutive system equations, and so is
usually slower, but as trade-off requires less
memory (to hold just one N by N matrix). The two
forms will lead to slightly different numerical
results, although tests documented in the third
reference given in Further Information show that
the differences are generally less than the
inherent discretization error itself and so are
not meaningful.
0 - symmetric form (default)
1 - nonsymmetric form
* * *
The CMIRS (Composite Method for Implicit Representation
of Solvent) model is a combination of SS(V)PE with the
DEFESR (Dispersion, Exchange, and Field-Extremum Short-
Range) model. It borrows use of a grid from the DFT code,
and therefore is currently implemented only for the $DFT
METHOD=GRID choice in $CONTRL: note that HF calculations
can be done with DFTTYP=HFX in $CONTRL. If default
parameters are desired (which correspond to water solvent,
an isodensity cavity with contour 0.001 au, and the
B3LYP/6-31+G* electronic structure method), then only the
IDEF flag needs to be set.
IDEF = flag to activate DEFESR calculations
0 - DEFESR energies are not computed (default)
1 - DEFESR energies are also computed
RHOSOLV = average electron density of solvent for use in
the dispersion model (default=0.05 au for water)
DISDMP = dispersion damping factor (default 7.0 bohr).
This value has been found to be nearly optimal
for all solvent/cavity/methods tested.
DISLIN = dispersion linear parameter
(default=0.0109369 au).
It is sensitive to the solvent/cavity/method.
EXCLIN = exchange linear parameter
(default=0.0460402 au).
It is sensitive to the solvent/cavity/method.
NGSLGR = order of Gauss-Laguerre numerical integration
used for the exchange term (default=6).
Possible values are 1 to 25.
FNNL,FPNL = field-negative and field-positive nonlinear
parameters (default=3.6 and 3.6). These values
have been found to be nearly optimal for all
solvent/cavity/methods tested.
FNLIN,FPLIN = field-negative and field-positive linear
parameters (defaults=-945.810 and -17.8279 au).
They are sensitive to the solvent/cavity/method.
For solvents like cyclohexane and benzene that
have negligible hydrogen-bonding capability they
can be set to 0.
SMVLE = flag to turn on an alternative (to DEFESR) semi-
empirical correction for local electrostatic
effects based on the electric field's normals to
the surface cavity. This also adds cavitation/
dispersion/solvent structure (CDS) effects drawn
from the SMD model, see SMD in $PCM.
(Default=.FALSE.)
* * *
The remaining parameters below are rather specialized
and rarely of concern. They should be changed from their
default values only for good reason by a knowledgeable
user.
TOLCAV = convergence criterion on maximum deviation of
calculated vs. requested RHOISO
(relevant if ISHAPE=0; default=1.0D-10)
ITRCAV = maximum number of iterations to allow before
giving up in search for isodensity surface.
(relevant if ISHAPE=0; default=99)
NDRCAV = highest analytic density derivative to use in the
search for isodensity surface.
0 - none, use finite differences (default)
1 - use analytic first derivatives
LINEQ = selects the solver for the linear equations
that determine the effective point charges on
the cavity surface.
0 - use LU decomposition in memory if space
permits, else switch to LINEQ=2
1 - use conjugate gradient iterations in memory if
space permits, else use LINEQ=2 (default)
2 - use conjugate gradient iterations with the
system matrix stored externally on disk.
CVGLIN = convergence criterion for solving linear equations
by the conjugate gradient iterative method
(relevant if LINEQ=1 or 2; default = 1.0D-7)
CSDIAG = a factor to multiply diagonal elements to improve
the surface potential matrix, S.
(default = 1.104, optimal for Lebedev integration)
IRDRF = a flag to read in a set of point charges as an
initial guess to the reaction field.
0 - no initial guess reaction field (default)
1 - read point charges from $SVPIRF input group.
It is up to the user to be sure that the
number of charges read is appropriate.
IPNRF = a flag to punch the final reaction field.
0 - no punch (default)
1 - punch in format of $SVPIRF input group
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generated on 7/7/2017