
SCRF Keyword

SOLVENT  ID  e 
Water [H2O]  1  78.39 
DiMethylSulfoxide [DMSO]  2  46.7 
NitroMethane  3  38.2 
Methanol [CH3OH]  4  32.63 
Ethanol [CH3CH2OH]  5  24.55 
Acetone [CH3COCH3]  6  20.7 
DiChloroEthane [CH3ClCH3Cl]  7  10.36 
DiChloroMethane [CH2Cl2]  8  8.93 
TetraHydroFuran [THF]  9  7.58 
Aniline  10  6.89 
ChloroBenzene  11  5.621 
Chloroform [CHCl3]  12  4.9 
EtherDiEthylEther  13  4.355 
Toluene  14  2.379 
Benzene  15  2.247 
CarbonTetrachloride [CCl4]  16  2.228 
CycloHexane  17  2.023 
Heptane  18  1.92 
Acetonitrile  19  36.64 
METHOD SELECTION OPTIONS
Dipole
Perform an Onsager model reaction field
calculation. This is the default.
PCM
Perform a PCM model reaction field calculation
using the polarizable dielectric model [155,
154, 343 ]. DPCM,
Tomasi and Pisa are synonyms for this option.
CPCM
Perform a PCM calculation using the polarizable
conductor calculation model [350]. Cosmo is a
synonym for this option.
IEFPCM
Perform a PCM calculation using the integral
equation formalism model [345, 347,352].
IPCM
Perform an IPCM model reaction field calculation.
Isodensity is a synonym for IPCM.
SCIPCM
Perform an SCIPCM model reaction field
calculation: perform an SCRF calculation using a cavity determined
selfconsistently from an isodensity surface. This is the default for single
point energy calculations and optimizations.
DIPOLE MODEL OPTIONS
A0=val
Sets the value for the solute radius in
the route section (rather than reading it from the input stream). If this
option is included, then Solvent or Dielectric must also be
included.
Dielectric=val
Sets the value for the
dielectric constant of the solvent. This option overrides Solvent if
both are specified.
PCM MODELS OPTION
Read
Indicates that a separate section of keywords and
options providing calculation parameters should be read from the input stream
(as described above).
IPCM MODEL OPTIONS
GradVne
Use Vne basins for the numerical integration.
GradRho
Use density basins for the numerical
integration. The job may fail if nonnuclear attractors are present.
SCIPCM MODEL OPTIONS
UseDensity
Force the use of the density matrix in
evaluating the density.
UseMOs
Force the use of MOs in evaluating the density.
GasCavity
Use the gas phase isodensity surface to
define the cavity rather than solving for the surface selfconsistently. This
is mainly a debugging option.
NoScale
Turn off scaling (designed to account for
charge outside the cavity) for the SCIPCM calculation. Scaling is performed by
default. NoScale reproduces the behavior of SCIPCM in Gaussian
94.
NUMERICAL SCRF OPTIONS
Numer
Force numerical SCRF rather than analytic. This
keyword is required for multiple orders beyond Dipole
Dipole
The options Dipole, Quadrupole,
Octopole, and Hexadecapole specify the order of multipole to use
in the SCRF calculation. All but Dipole require that the Numer
option be specified as well.
Checkpoint
Begin the numerical SCRF with a previously
computed reaction field from the checkpoint file. This is synonymous with
Field=EChk.
Cards
Begin the numerical SCRF with a previously
computed reaction field read from the input stream, immediately after the line
specifying the dielectric constant and radius (three freeformat reals).
AVAILABILITY AND RESTRICTIONS
The Onsager model is available for HF, DFT, MP2, MP3, MP4(SDQ), QCISD, CCD, CID, and CISD energies, and for HF and DFT optimizations and frequency calculations.
The PCM and IPCM models are available for HF, DFT, MP2, MP3, MP4(SDQ), QCISD, CCD, CID, and CISD energies only.
The SCIPCM model is available for HF and DFT energies and optimizations and numerical frequencies.
The Opt Freq keyword combination may not be used in SCRF calculations.
SCRF=PCM and SCRF=IPCM jobs can be restarted from the checkpoint file by using the Restart keyword in the job¹s route section. SCRF=SCIPCM calculations which fail during the SCF iterations should be restarted via the SCF=Restart keyword.
RELATED KEYWORDS
EXAMPLES
The energy computed by an Onsager SCRF calculation appears in the output file as follows:
Total energy (include solvent energy) = 74.95061789532
Energy output from the other SCRF models appears in the normal way within the output file, followed by additional information about the calculation. For example, here is the section of the output file containing the predicted energy from a PCM calculation:
IN VACUO Dipole moment (Debye): X= 0.0000 Y= 0.0000 Z= 2.0683 Tot= 2.0683 IN SOLUTION Dipole moment (Debye): X= 0.0000 Y= 0.0000 Z= 2.1876 Tot= 2.1876 SCF Done: E(RHF) = 100.029187240 A.U. after 5 cycles Convg = 0.4249D05 V/T = 2.0033 S**2 = 0.0000   VARIATIONAL PCM RESULTS  <Psi(0)HPsi(0)> (a.u.)= 100.024608 <Psi(0)H+V(0)/2Psi(0)> (a.u.)= 100.028947 <Psi(0)H+V(f)/2Psi(0)> (a.u.)= 100.029186 <Psi(f)HPsi(f)> (a.u.)= 100.023819 <Psi(f)H+V(f)/2Psi(f)> (a.u.)= 100.029187 Total free energy in sol. (with non electrost. terms (a.u.)= 100.028994  (Unpol. Solute) Solvent (kcal/mol) = 3.06 (Polar. Solute) Solvent (kcal/mol) = 3.37 Solute polarization (kcal/mol) = 0.16 Total Electrostatic (kcal/mol) = 3.21  Cavitation energy (kcal/mol) = 3.20 Dispersion energy (kcal/mol) = 4.12 Repulsion energy (kcal/mol) = 1.04 Total non electr. (kcal/mol) = 0.12  DeltaG (solv) (kcal/mol) = 3.09 
Note that the PCM results also include the dipole moment in the gas phase and in solution, the various components of the predicted SCRF energy and DG^{solvation}.
For all iterative SCRF methods, note that the energy to use is the one preceding the Convergence achieved message (i.e.,one from the final iteration of the SCRF method).
INPUT SYNTAX AND KEYWORDS FOR PCM CALCULATIONS
The following
keywords are available for controlling PCM calculations (arranged in groups of
related items):
SPECIFYING THE SOLVENT
The solvent for the PCM calculation
may be specified using the normal Solvent option to the SCRF
keyword. The solvent name keyword or ID number may also be placed within the
PCM input section. Alternatively, the EPS and RSOLV keywords may
be used in the PCM input section to define a solvent explicitly:
EPS=e
Dielectric constant of the solvent.
RSOLV=radius
Solvent radius in Angstroms.
EPSINF=val
Optional value for the dielectric
constant at infinite frequency.
CALCULATION METHOD VARIATIONS
NODIS
Skip the calculation of dispersionrepulsion
solute solvent interaction.
NOCAV
Skip the calculation of cavitation energy.
DUMP
Provide verbose output as the calculation
progresses.
NOSCFVAC
Skip the gas phase calculation before that in
solution. While this saves some computation time, it prevents the calculation
of DG^{solvation}, the variation of
the dipole moment in solution, and so on.
FIXCAV
Compute the electrostatic energy gradients
neglecting the geometrical contributions (i.e., at "fixed cavity"). Be aware
that the geometrical contributions are always included in the calculation of
nonelectrostatic energy gradients (the latter gradients can be skipped with
NOCAV and NODIS).
ACCPCM=val
Accuracy threshold for the calculation of
electric potential on the cavity. The default value is 10^{6}.
TABS=temp
Temperature in Kelvin. The default value is
298.15. Note that you must also specify the correct value of the dielectric
constant (episilon) at that temperature using the EPS keyword.
CHARGE NORMALIZATION
ICOMP=N
Specifies the method used to normalize the
polarization charge to get the value predicted by Gauss' law. N can take on the
following values:
 1. The difference between the calculated and the theoretical (Gauss) polarization charge is distributed on each tessera proportionally to its area.
 2. The calculated charge on each tessera is scaled by a constant factor.
 3. The charge difference is distributed according to the solute electronic density on each tessera.
 4. The effect of outlying charge is accounted for by means of an additional effective charge, distributed according to the solute electronic density.
Normally, the default is 4 for single point calculations and 2 for geometry optimizations (this one being the only method allowing the calculation of gradients). For CPCM (which is less affected by the outlying charge effects), the default is always 2.
SPECIFYING CHARACTERISTICS OF THE CAVITY
By default, the program builds up the cavity by putting a sphere around each solute heavy atom; hydrogen atoms are always enclosed in the sphere of the atom to which they are bonded; the radius of the atom is increased by a constant amount for each bonded hydrogen atom, up to a maximum of 3 (the increase is0.9 for secondrow atoms, 0.13 for thirdrow atoms, and 0.15 for atoms in higher rows). Explicit hydrogen atoms can be added by specifying the UFF atom type within the molecule specification, as in this example.
RADII=UAHF
Use the United Atom Topological Model [346] to build the cavity, automatically set by the
program according to the molecular topology, hybridization, formal charge, etc.
Note that hydrogens don't have individual spheres defined and that these radii
were optimized for the HF/631G(d) level of theory.
RADII=UFF
Use atomic radii from the UFF force field.
RADII=BONDI
Use Bondi¹s atomic radii.
RADII=PAULING
Use Pauling's (actually MerzKollman)
atomic radii.
ALPHA=scale
Specify the scaling factor (for
all the elements but acidic hydrogens) for the definition of solvent accessible
surfaces. In other words, the radius of each atomic sphere is determined by
multiplying the van der Waals radius by scale. The default value is 1.2.
ALPHAH=hscale
Specify the scaling factor for
acidic hydrogens (automatically recognized by the program as those bonded to N,
O, P or S halogens). The default value is 1.0.
RET=len
Sets the minimum radius (in Angstroms)
of the "added spheres". Increasing this parameter causes the number of added
spheres to decrease (for example, to inhibit the creation of added spheres, use
RET=100). The default value is 0.2.
NSFE=n
Sets the number of initial spheres
(useful if this number is not equal to the number of solute atoms, e. g. if a
methyl group is enclosed in one sphere, and so on). When included, the program
looks for the positions and the radii of the n spheres in an additional input
section following the PCM input (this section is also blankterminated).
The spheres can be defined using lines in either of the following formats:
N1 [radius [scale hscale]] X Y Z [radius [scale hscale]]
In the first case, the line specifies an atom number and (optionally) the sphere radius and one or both scaling factors for that atom. In the second case, used to define arbitrary spheres, the Cartesian coordinates of the center of the sphere are again optionally followed by its radius and scaling factors. If parameters are omitted, then the standard values are used automatically. Note that lines of different formats can be freely intermixed in this input section as the program will automatically determine the syntax based on the number and types of parameter specified on any given line.
SELECTING THE POLYDEDRON FOR THE SURFACE TESSERAE
In standard calculations the surface of each sphere is subdivided in 60 triangular tesserae, by projecting the faces of an inscribed pentakisdodecahedron. Other polyhedra with a different number of faces can be used, to get rougher or finer descriptions of the surface, by using one of these keywords:
TSNUM=N
Sets the number of tesserae on each
sphere (60 is the default for the usual pentakisdodecahedron). The program
automatically selects the polyhedron with the closest number of faces to the
specified value of N.
TSARE=area
Specifies the area of the tesserae,
in units of Å^{2} (0.4 is a typical value). The program
automatically determines the best polyhedron for each sphere.
EXAMPLE PCM INPUT
The following Gaussian job performs a PCM energy calculation on the molecule HF using the solvent cyclohexane. The calculation is performed at a temperature of 300 K using a scaling factor for all atoms except acidic hydrogens of 1.21 and a value of 70 tesserae per sphere:
# HF/631++G(d,p) SCF=Tight SCRF=(PCM,Read,Solvent=Cyclohexane) Test PCM SP calculation on hydrogen fluoride 0,1 H F 1 R R=0.9161 TABS=300.0 ALPHA=1.21 TSNUM=70
The final input section ends as usual with a blank line.