These values are printed in the output. It should be noted that in the output two different equations are used to calculate polarizabilities. (E4 is the energy equations and 'dip' is the dipole equationfrom the Kurtz paper.) The main difference between these methods is sensitivity to 'round off' error. The difference can be used as an estimate of the uncertainity in the final results.
Additional polarizability terms can also be entered into the spreadsheet with the "Term=@PROP(POLAR_SUMMARY,i)" function, where 'i' can be 1,2, or 3 for 'alpha', 'beta' or 'gamma', respectively. The six unique terms in the polarizability tensor can be accessed via the "Term=@PROP(POLAR_TENSOR,i)" function. Functions should be typed into an empty column header cell in the Spartan spreadsheet. Characters to the left of the equal sign (=) will become the displayed 'label' for the new column.
electronegativity: ( E_HOMO + E_LUMO )/2 hardness : ( E_HOMO  E_LUMO )/2 polarizabilty : 0.08 * VdW_Volume 13.0352*hardness + 0.979920*hardness^2 +41.3791 The final units are in 10^30 m^3
Rather than units of:
coul*m^2/energy
We divide by the permittivity of free space (and 4*pi)
and then scale to units appropriate to the atomic scale.
Where do those terms come from?
Though these
coefficients may appear arbitrary, the first term
is derived from an estimation that assumes all atoms have the
polorizability of hydrogen,
with a correction applied from the energy gap of the highest occupied &
lowest unoccupied molecular orbitals. This equation is only used in the
semiempirical methodsand it turns out that this is a fairly good
first guess. From a freshman physics textbook, the answer should
be (for atomic groups):
H 0.66 He 0.21 Li 12 Be 9.3 C 1.5 Ne 0.4 Na 27 Ar 1.6 K 34
Qplus & Qminus are known as the 'TLSER' parameters.
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O = A/(4*pi*((3*V)/4*pi)^(2/3)) where A : Area V : Volume O : OvalityThus the He atom is 1.0 and HC24H (12 triple bonds) is ~1.7.
electronegativity  = (HOMO + LUMO)/2 
hardness  = (HOMO  LUMO)/2 
"LogP" methods can be selected with the LOGP= keyword;
LOGP=VILLAR and LOGP=GHOSE
respectively.
Spartan includes a number of ways to examine solvation.
We currently implement the CramerTruhlar SM54P and SM54A solvation methods for water. This solvation calculation is done, by default, for all quantum mechanics calculations which have SM5 parameterized atoms. The energy of solvation predicted by this model can be found in the output text. The "solvated energy" (calculated by adding the electronic energy and the solvation energy) is labeled as "Energy(Aq)" in the spreadsheet window and in the molecule properties dialogue.
Literature on these methods is extensive,
some important articles are:
SM50R is a solvation method derived from the semiempirical SM54 approach described above. It is independent of the wavefunction and depends only on the geometry of the molecule. As such, it is very fast and is applicable to large systems and molecular mechanics calculations. This method can be accessed by using the POSTSOLVENT=SM50R keyword.
MMFFaq is an extension to the MMFF94 forcefield, in which the SM50R energy term is added to the molecular mechanics energy. In Spartan, the MMFFaq forcefield is implemented such that the solvation energy is only added AFTER the geometry has been optimized. Thus the structures of molecules from MMFF94 and MMFFaq calculations will be the same, but their energies will be different. Thus, the MMFFaq method is most useful in the context of conformational searching or energy profile as the energy ordering of any conformers will likely be different in water (MMFFaq) than in vacuum (MMFF94).
The SM8 model allows both water and organic solvents and treats both neutral and charged solutes. This method is notable for the large suite of experimental data used to parameterize the model and uses the HF or DFT wavefunctions. To run SM8 as a property calculation (to calculate the energy of solvation) use the keyword POSTSOLVENT=WATER where water can be replaced with many different organic solvents. The list of supported solvents is as follows:
WATER, 111TRICHLOROETHANE, 112TRICHLOROETHANE, 11DICHLOROETHANE, 124TRIMETHYLBENZENE, 14DIOXANE, 1BROMO2METHYLPROPANE, 1BROMOPENTANE, 1BROMOPROPANE, 1BUTANOL, 1CHLOROPENTANE, 1CHLOROPROPANE, 1DECANOL, 1FLUOROOCTANE, 1HEPTANOL, 1HEXANOL, 1HEXENE, 1HEXYNE, 1IODOBUTANE, 1IODOPENTENE, 1IODOPROPANE, 1NITROPROPANE, 1NONANOL, 1OCTANOL, 1PENTANOL, 1PENTENE, 1PENTYNE, 1PROPANOL, 222TRIFLUOROETHANOL, 224TRIMETHYLPENTANE, 24DIMETHYLPENTANE, 24DIMETHYLPYRIDINE, 26DIMETHYLPYRIDINE, 2BROMOPROPANE, 2CHLOROBUTANE, 2HEPTANONE, 2HEXANONE, 2METHYLPENTANE, 2METHYLPYRIDINE, 2NITROPROPANE, 2OCTANONE, 2PENTANONE, 2PROPANOL, 2PROPEN1OL, 3METHYLPYRIDINE, 3PENTANONE, 4HEPTANONE, 4METHYL2PENTANONE, 4METHYLPYRIDINE, 5NONANONE, ACETICACID, ACETONE, ACETONITRILE, ANILINE, ANISOLE, BENZALDEHYDE, BENZENE, BENZONITRILE, BENZYLALCOHOL, BROMOBENZENE, BROMOETHANE, BROMOOCTANE, BUTANAL, BUTANOICACID, BUTANONE, BUTANONITRILE, BUTYLETHANOATE, BUTYLAMINE, BUTYLBENZENE, CARBONDISULFIDE, CARBONTET CHLOROBENZENE, CHLOROTOLUENE, CIS12DIMETHYLCYCLOHEXANE, DECALIN CYCLOHEXANE, CYCLOHEXANONE, CYCLOPENTANE, CYCLOPENTANOL, CYCLOPENTANONE, DECANE, DIBROMOMETHANE, DIBUTYLETHER, DICHLOROMETHANE, METHYLCHLORIDE, DIETHYLETHER, DIETHYLSULFIDE, DIETHYLAMINE, DIIODOMETHANE, DIMETHYLDISULFIDE, DIMETHYLACETAMIDE, DIMETHYLFORMAMIDE, DMF, DIMETHYLPYRIDINE, DMSO, DIMETHYLSULFOXIDE, DIPROPYLAMINE, DODECANE, E12DICHLOROETHENE, E2PENTENE, ETHANETHIOL, ETHANOL, ETHYLETHANOATE, ETHYLMETHANOATE, ETHYLPHENYLETHER, ETHYLBENZENE, ETHYLENEGLYCOL, FLUOROBENZENE, FORMAMIDE, FORMICACID, HEXADECYLIODIDE, HEXANOIC, IODOBENZENE, IODOETHANE, IODOMETHANE, ISOBUTANOL, ISOPROPYLETHER, ISOPROPYLBENZENE, ISOPROPYLTOLUENE, MCRESOL, MESITYLENE, METHANOL, METHYLBENZOATE, METHYLETHANOATE, METHYLMETHANOATE, METHYLPHENYLKETONE, METHYLPROPANOATE, METHYLBUTANOATE, METHYLCYCLOHEXANE, METHYLFORMAMIDE, MXYLENE, HEPTANE, HEXADECANE, HEXANE, NITROBENZENE, NITROETHANE, NITROMETHANE, METHYLANILINE, NONANE, OCTANE, PENTANE, OCHLOROTOLUENE, OCRESOL, ODICHLOROBENZENE, ONITROTOLUENE, OXYLENE, PENTADECANE, PENTANAL, PENTANOICACID, PENTYLETHANOATE, PENTYLAMINE, PERFLUOROBENZENE, PHENYLETHER, PROPANAL, PROPANOICACID, PROPANONITRILE, PROPYLETHANOATE, PROPYLAMINE, PXYLENE, PYRIDINE, PYRROLIDINE, SECBUTANOL, TBUTANOL, TBUTYLBENZENE, TETRACHLOROETHENE, THF, TETRAHYDROFURAN, TETRAHYROTHIOPHENEDIOXIDE, TETRALIN, THIOPHENE, THIOPHENOL, TOLUENE, TRANSDECALIN, TRIBROMOMETHANE, TRIBUTYLPHOSPHATE, TRICHLOROETHENE, TRICHLOROMETHANE, TRIETHYLAMINE, UNDECANE, Z12DICHLOROETHENE
The solvents in bold are availble from the pulldown'insolvent' menu. It is important to notice that no spaces are allowed in the name, thus "acetic acid" is spelled "ACETICACID".
The reference for SM8 is
A.V. Marenich, R.M. Olson, C.P. Kelly, C.J. Cramer,
D.G. Truhlar,
"SelfConsistent Reaction Field Model for Aqueous and
Nonaqueous Solutions Based on Accurate Polarized Partial
Charges,"
J. Chem. Theory Comput. 3, 2011 (2007)
The Surface and Simulations of Volume Polarization for Electrostatics (SS(V)PE) method treats the solvent as as a continuum dielectric, solving Poisson's equation on the boundary. A dielectric constant is needed for the calculation. For example, POSTSOLVENT=SVP,78.39 would be use for water. References for this method can be found in
It should be noted that analytical gradients are not available, so transition state searches with this solvent model should only be applied to small molecules. Another important constraint of our implementation is that only molecules with 'starlike' volumes are allowed. Any ray emanating out from the center can only pass through the surface once.
Our implmentation has been designed for small molecules. So for larger molecules one may have to modify internal parameters to get good results. Specifically NPTLEB=, which controls the number of Lebedev points set to 1202. This has been shown to be precise enough for .1 kcal/mol on solutes the size of monosubstituted benzenes. Other possible lvalues are (974,1202,1454,1730,2030,2354,2702,3074,3470,3890,4334,4801,5294).
For legacy purposes Spartan also implements the CramerTruhlar SM3 method. The SM54P and SM8 method are much improved over SM3 and should not be used in the future, but can be accessed with the POSTSOLVENT=SM3 keyword.
We use the POSTSOLVENT keyword to do a energy of solvation calculation. By default Spartan 08 has an implied POSTSOLVENT=SM54 to calculate the energy of solvation for any molecule which has atoms parameterized for SM54. This does a quick semiempirical calculation (or SM50R for molecular mechanics jobs) at the end of the main calculation step. The resulting free energy of solvation is displayed in the output and the combined energy is available in the molecule properties panel with the "Energy(aq)" label. This calculation is also useful to determine the energy differences among different conformers of the same molecule as the bond lengths and angles do not change signifanctly solvent is added.
If one want's to see the affect of solvation on the geometry, (for example for a transition state structure) the ADDSOLVENT= should used. This is what the "insolvent" pull down menu in the calculation panel does (for HF and DFT calculations). SOLVENT= is a synonym for ADDSOLVENT=, but if typed in will be erased from the option line and the "insolvent" pulldown menu will be modified to match what was typed in.
The CramerTruhlar methods (SM8, SM54, SM50R, SM3) work only with common organic atoms: H, C, N, O, F, S, Cl, Br, and I. (SM8 adds Si and P if bonded to oxygen.) The calculation may proceed with other elements, but important terms of the approximation will be set to zero. If the atoms "aren't very important" relative solvation energies of conformers might be useful, but absolute values will be poor.
The SS(V)PE method is not parameterized and is available for any atom of the underlyling basisset.
In more recent versions of Spartan, the output includes two sets of electrostatic charges. The traditional method calculates a charge for each atom. The newer method places a charge, a dipole, a quadrapole and an octopole on each heavy atom. (We are using these later values in internal projects.) The use of atomic dipoles does a better job of modeling the electrostatic potential.
If the printing of charges is turned on 'Q0' represents the atomic charge; 'Qx', 'Qy' and 'Qz' represent the atomic dipole; 'Qxx', 'Qxy', etc. are the components of the traceless qudrapole.
Spartan's ESP charge calculation is based on the 'CHELP'
algorithm.
In this algorithm the charges at the atomcenters are chosen
to best describe the external field surrounding the molecule.
Ideally this area should include everything outside of the Van der
Waal radii. Of course this would be time consuming and may
work too hard to get very exact longrange dipole terms at the
cost of inaccuracies in the field near the atom. As a compromise,
a shell surrounding the atoms is used. The thickness of this shell
is 5.5 au. This default value can be modified using the SHELL=
keyword in the Options field of the Calculations dialogue.
You may also change the inner value of this shell from the VDW
to (VDW + WITHIN) with the keyword WITHIN=.
Keyword  Description  Default 
SHELL=  The farthest extent of the shell of points to used to fit the electrostatic potential.  5.5 
WITHIN=  A buffer between the standard VdW radii and the nearest points in the shell of external points.  0.0 bohrs 
ELCHARGE=  An integer number representing the number of points per cubic Bohr.  1 
CHELPDENSITY=  An integer number representing the number of points per cubic Bohr.  1 
SVD=  Use the CHELPSVD (Single value decomposition) algorithm
to calculate the charges. Setting to 0 turns off. There
are a number of variants to this algorithm:

0 
SVDTHRESH=  .00001  
CHELPPOINTS=  Algorithm which places points into the shell.
 1 
CHELPEXTRA=  Choose more points than just nuclei. This
allows one to approximate a multipole expansion around
each nuclei.
 0 
Relevant references:
More information from NBO calculations can be printed with the keyword PROPPRINTLEV=2. This may be useful if problems are detected with the NBO calculation. There are known problems with Spartan's implementation of natural bond order calculations on large delocalized systems.
The overlap matrix is the overlap of different atomic orbitals. It can be printed with the PRINTOVERLAP keyword. The ordering of the coefficients is the same as that displayed for the molecular orbitals when the "Print: Orbitals & Energies" check box is selected.
The default masses are found in the "MASS.spp" parameter file. ("params.MASS" on Unix/Linux machines.) The default value is the mass of the most common isotope. This can be overriden with the AVGMASS keyword, or by changing the isotope of a specific atom in the Property dialogue..
The units of absorbance is kilometers per mol, km/mol. The justification for this unit can be surprising, so we derive here. The molar absorption coefficient e
where C is the concentration, (mol/L), d is the path length (cm), Io/I is the intensity ratio (unitless, incedent over transmitted) and and 'v' is the wavenumber (1/cm). Thus the unit is
However, what is measuresd is the integration absorption A
Full Spartan can generate a reaction path using three approaches. The simplest is via the 'energy profile' calculation, which changes specific coordinates. (See the discusion of energy profile.) This works well for simple systems when the reaction coordinate can be well represented as internal coordinates (such as bond distance).
A reaction path can also be generated by the calculation of the Transition State Geometry along with a frequency calculation. A list file can be generated for the signle imaginary frequency corresponding to the reaction coordinate.
Spartan has also implemented a reaction coordinate algorithm to generate a reaction path given a transition state using the algorithm by Schmidt. (M.W. Schmidt, M.S. Gordon, M. Dupuis, J. Am. Chem. Soc. (1985), 107, 2585) This can be specified by checking the IRC button when performing a transition state geometry calculation. When selected, a new file will be generated that contains the reaction path.
The IRC calculations are time consuming. It is suggested that users confirm that a 'good transition state' has been found before resubmitting the with the IRC algorithm enabled. Confirm both, that the gradient is small and that there is only 1 negative eigenvalue.
Keywords related specifically to IRC calculation can be found in the keyword section.
The UV/Vis spectra is calculated by running a single point CIS calculation (or TDDFT calculation for DFT methods) after the main wavefunction has been calculated. In CIS theory, the absorption energies are the difference between the HF ground state and CIS excited state energies. A reference for Spartan's CIS implementation:
J.B. Foresman, M. HeadGordon, J.A. Pople, M.J. Frisch, J. Phys. Chem. (1992), 96, 135.
For DFT calculations, excited states are obtained using time dependent DFT calculations:
E. Runge, U. Gross, Phys. Rev. Lett. (1984) 961533] A CISlike TammDancoff approximation [S. Hirata, M. HeadGordon, Chem. Phys. Lett. (1999) 302 375S.
Hirata, M. HeadGordon, Chem. Phys. Lett. (1999) 314 291
This calculation is similar to the CIS calculation, and most keywords controlling the excited state CIS calculation are used in the TDDFT calculation.
A UV/Vis calculation is done, by default, whenever a singlepoint excited state calculation is specified. If one needs to modify the UV/Vis calculation, (other than with the UVSTATES keyword) a single point excited state calculation must be performed, using the keywords described below.
See the keyword section on CIS/TDDFT for relevant keywords. If you want a geometry optimization for something other than the first excited state, use the ESTATE=n keyword to choose a different excited state.
It should be noted that information on each excitation can be found in the verbose output. The notation
The Transition dipole moment and oscillator strength are also printed. The oscilator strenghts are used by Spartan to graphically display the UV/Vis spectrum. To convert the oscillator strength to absorbance, we divide by 4.319x10^{7}. Usually the log (base 10) of the absorbance is used to display the spectrum.
By default only pairs of filled/unfilled orbitals which have amplitudes larger than 0.15. To see more components you can use the CIS_AMPL_PRINT=1 keyword to see (nearly) all of the components. The sum of the square of all components will add to 1.0.
The score used for alignment is designed to be 1 for a perfect fit and 0 for a terrible fit. For a system with N centers:
'r_{i}' is the i'th center of the trial molecule, and
'ro
The second equation is used when (r_{i}ro_{i})/R_{i} is greater than 1.0. The normalizing R_{i} is (3/5) of the VanderWall radii for atoms, and for CFD's is the radii given in the property panel when a CFD is selected.
The distinguishing feature of this function when compared to a simple RMSD type function ((r_{i}ro_{i})^{2} is that in the case where most of the centers will line up exactly, but only 1 is nowhere near matching, the latter center will adversely affect the alignment of the former centers. As an example, let try to map the H2 molecule onto a template of the Br2 molecule with R_{Cl} set anomolously small, say 1/10 of a angstorm. The 'best' (and only) minima found by the RMSD function is the H2 molecule centered symmetrically at the center of the Br2 molecule. The score we use would find an offcenter minima with one hydrogen directly on one Bromine, and the other Hydrogen near the center of the Br2 molecule.
When aligning two separate sets of centers, a number of alignments are examined. It should be noted that the 6dimensional translation/rotation space of the above function can have many local minima, or alignments. These are minimized and examined, and the best one is returned. Also, a second score is used internally: 'the number of 'matched centers'. This score closely matches the reported score, but any alignment in which some centerpairings do not line up with R_{i} are rejected, prior to comparing actual score values.
^{1} Indicates that these should not be typed in as there is a button in the calculation dialogue for it. ^{2} The keyword is used by a module other than the property module, but is mentioned here for completeness.  
PROPPRINT=i PROPPRINTLEV=i  For 'i' greater than 1, print more information into the output file. 'i' must be 4 or less  0 
PRINTCOORDS  Print the cartesian coordinates of all atoms in the system.  
ACCEPT  Accept certain error conditions and continue without a fatal error.  
BTABLE=BAD  Print out a table on all bond distances (B), bond angles (A) and dihedral (D) angles. If only bond distances, angles or dihedrals are required, BAD can be replaced with B, A, or D respectively.  
NEAREST=x.y  Specify the multiplication factor (applied to nearestneighbor distances) when generating the geometric information.  1.2 
QSAR 
Prints various QSAR descriptors. While these values are
usually calculated, and can be found in the proparc file and
in the spreadsheet this prints them to the output file.
The list of descriptors this keyword prints is:
 
NOQSAR  Skip the calculation of QSAR descriptors.  
MOMENTS  Print out the moments of inertia, in both atomic units and inverse centimeters.  
MAXVOLSIZE=i  Atomic volumes and surface areas will be calculated only for systems with fewer than 'i' atoms.  100 
SOLVRAD  In calculation of atomic areas and volumes, add this value to the VdW radii.  
VPTS=i AARCS=j APTS=k  To control the internal working of the volume calculator.  
POSTSOLVENT=xxx^{2} ADDSOLVENT=yyy^{2} SOLVENT=zzz^{1,2} 
To select different solvation models. See the discussion on solvent methods and the SOLVENT= keyword.  
TESTPROPS=1 
Internal keyword used for debugging and QA work at
Wavefunction. This works on the 'cell' data of the spreadsheet.
Cells with the following names are analyzed:
 
PARCFORMAT=i 
[for internal to wavefunction use] If i=1 write both formats of frequency information. If i=2 write only new format of frequency information.  i=2 
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PRINTMO^{1}  Print the Molecular orbitals.  
PRINTORBE ORBE  Print molecular orbital energies  
PRUNEVIRTUAL=x PRUNEVIRTUAL=NONE 
Delete unoccupied molecular orbitals 'x' above the LUMO. This is useful in decreasing the size of the molecular data stored on the disk and in making the output of PRINTORBE and PRINTMO more reasonable.  10 
POSTHF  Use the post hartreefock wavefunction if available. On by default for MP2 type calculations.  
NOPOSTHF  Do not use the post HF calculations. For MP2 this means, to use the HF wavefunction instead of the corrected MP2 wavefunction,  
IGNOREWVFN  Skip all wavefunction dependent properties.  
NBO NBO=yy 
Do the natural bond order hybridization analysis. See the
above discussion. Possible values
for yy are:
 
MULPOP^{1} PROP:MULPOP=3 
Print the Mulliken charges. With a value of 3, the full matrix is printed,  1 
NOMULCHARGE NOMULPOP  Skip the mulliken charge calculation  
POP^{1}  Print the natural atomic charges  
NONATCHARGE  Skip the natural atomiccharge calculation  
DEORTHOG  Deorthogonalize semiempirical MOs before calculating properties.  
DIPOLE  Print out the Cartesian components of the dipole moment  
NODIPOLE  Skip the calculation of the dipole moment.  
BONDORDER  Print out Mulliken and Lowdin bond order matrices, plus atomic and free valencies for openshell wavefunctions.  
PRINTNBO  Print the AO to NBO transformation  
NOPOP  Skip the natural bond order (NBO), and natural charge calculation.  
DOEPN  Print out the "Eletronic Potential at Nuclie" for Oxygen and Nitrogen. DOEPN=SKIP to skip calculation. (By default the calculation is stored in archive but not printed. Enter DOEPN=ALL to print all atoms.  
PRINTS  Print the atomic orbital overlap matrix (S).  
LOGP=  See the discussion on the LogP calculation  
ELP  Specify that the elpot+polpot grid will be used to generate atomic charges. This is valid for closedshell HFonly molecules.  
PRINTOVERLAP PRINTS  Print the overlap matrix as a lower triangle. Use in conjuction with the "Print: Orbitals & Energies" check box if you want to do your own 'homebrew' quantum mechanics calculation. See the discussion of atomic orbitals for more information. (The PRINTS is spelling is deprecated.)  
USEQCPOT  
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NOFREQ  Do not do any frequency or thermodynamic calculation even if there is a good Hessian. (By default, if a high quality Hessian is available frequencies will be calculated.  
FREQSCALE=x FSCALE=x  Scale all the frequencies by a factor 'x'.  
DROPVIBS=x  When calculating thermodynamics values, ignore all modes with frequencies below 'x'.  
CLAMPTHERMO CLAMPTHERMO=x  When calculating thermodynamics values, clamp enthalpy terms at 'x'RT. (If no 'x' given 1/2 is used.) Entropy and the heat capacity will be clamped at 'x'R. For 'x'=1/2 these limits imply a break in the enthalpy, entropy and heat capacity at ~260 cm^{1}, ~116 cm^{1} and ~2 cm^{1} respectively.  
PRINTMODE  Print thermodynamic information for each mode  
TEMPERATURE=  Change the default termerature used in the thermodynamic calculation.  298.15 K 
PRESSURE=  Change the default pressure used in the thermodynamic calculation.  1.0 atm 
PRINTFREQ^{1}  Print the Cartesian values of the normal mode vibrations. This is what the 'Print Virbrational Mode' button in the calculation dialogue panel controlls.  
THERMO^{1}  Print standard thermodynamic data. This is the 'Print Thermodynamics' button in the calculation dialogue.  
PRINTIR  Print Infrared and thermodynamic information for each normal mode vibration.  
AVGMASS  Use the terrestrial average mass of atoms when doing thermodynamics calculations. The default is to use the most common isotope. (Changing the isotope of a specific atom overrides the mass for only that atom.)  
APPROXFREQ  Calculate frequency and thermodynamic information on the intermediate low quality Hessian. (Not recommended.)  
GXTHERMO  Calculate G3 type results. (Internal keyword, should not be used unless you know what you are doing.)  
FREQ^{1,2} FREQ=CD^{2} FREQ=FD^{2} 
Calculate frequencies by numerical differentiaion, using central differences (CD) or forward differences (FD) as opposed to analytically. Analytical methods are usually much faster and more accurate than numerical methods as numerical methods requires 6 single point calculations for each atom in the molecule. Forward difference is usually %50 faster than central differences, but is significantly less accurate and is not recommended. The default is to use analytical frequencies if available.  
NUMERICALFREQ  Calculate frequencies by numerical differentiaion, using central differences. Analytical methods are usually much faster and more accurate than numerical methods as numerical methods requires 6 single point calculations for each atom in the molecule.  
FD=xx.yy^{2}  Step size for for numerical differentiation.  0.005 bohr 
^{Back to Top} See How can I control the parameters of the ESP model? for more details and some more keywords  
ELCHARGE^{1}  Print information about the electrostatic charges.  
NOELCHARGE  Skip the electrostatic charge calculation.  
CHELPPRINT=i  Print more information about the ESP charge calculation. Integers greater than 1 cause successivly more printing. Also available are TERSE  1 
^{Back to Top} See How can I use the Intrinisic Reaction Coordinate procedure? for more details  
IrcSteps=^{2}  Specifies the maximum number of points to find on the reaction path. (Should be odd. The default value of 41 yeilds 20 steps forward and 20 backwards.)  41 
IrcStepSize=^{2}  Specifies the maximum step size to be taken. This is in thousandths of a Bohr. The default of 150 means 0.15 Bohr.  150 
RPATH_TOL_DISPLACEMENT=^{2}  Specifies the convergence threshold for the step. If the atoms are moving less than this value, configuration is assumed to be at a minima and the algorithm will stop. The units are in millionths of a Bohr. The default value of 5000 corresponds to 0.005 Bohr.  5000 
^{Back to Top} see Controlling an excited state calculation  
ESTATE=n^{1,2}  Choose the excited state to calcualte the gradient for. Usualy this is not entered as a keyword, but is selected by choosing 'First Excited State' in the calculation dialogue.  1 
FULLTDDFT  By default the TDA approximatino is used in TDDFT calculations. This keyword will do the "Full" TDDFT calculation when doing excited states with DFT methods.  NO 
CIS_N_ROOTS=^{2}  To examine more orbitals in the excitation. For systems where there are many delocalized atoms you may want to increase this number from the default. Despite the "CIS" in this keywords spelling, it is also appropriate for TDDFT calculations.  >=5 
UVSTATES=^{2}  To examine more orbitals in the UV/Vis calculations. For systems where there are many delocalized atoms you may want to increase this number from the default. Only valid when the "UV/Vis" button is selected.  >=5 
INCLUDETRIPLETS^{2}  To include triplets in the UV/Vis calculation of singlet wavefunctions. The intensity of the these excitation will be small (zero) but can be useful if interested in all lower energy excited states.  
INCLUDESINGLETS^{2}  To include singlet excitations in the UV/Vis calculation of triplet wavefunctions. The intensity of the these excitation will be small (zero) but can be useful if interested in all lower energy excited states.  
CORE=FROZEN^{2}  By neglecting core electrons the calculation can be speeded up.  
N_FROZEN_VIRTUAL=n^{2}  Reduces the number of virtual molecular orbitals used in the calculation. Changing this number from the default, may speed up the calculation, but may also cause inaccuracies in the calculation.  
MAX_CIS_CYCLES=n^{2}  To change the number of SCF cycles to try before 'giving up' on the CIS calculation. Increase if you are having convergence problems, but waiting longer might work.  10 
CIS_CONVERGENCE=x^{2}  Decrease this number if you want quicker convergence at the cost of precision. (Reducing to a number below 5 can give unphysical results.)  6 
CIS_AMPL_PRINT=x  To print filled/unfilled molecuar orbital pairs which have coefficients larger than x. (This will go in the verbose output file, so make sure to use the KEEPVERBOSE keyword.)  15 