Spartan '14 Help  
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Properties FAQ
Questions About Spectra:Other QuestionsBack to Top Spartan can calculate polarizability in 3 ways:
Back to Top Polarizability calculated in the properties module is derived from an empirical formula: electronegativity: ( E_HOMO + E_LUMO )/2 hardness : ( E_HOMO  E_LUMO )/2 polarizability : 0.08 * VdW_Volume 13.0352*hardness + 0.979920*hardness^2 +41.3791 The final units are in 10^{30} m^{3}Electron Densities, Spin Densities, Dipole Moments, Charges and Electrostatic Potentials To get the more traditional units of coul^{2}*m/N We divide by the permittivity of free space (and 4*π) and then scale to units appropriate to the atomic scale. To convert from "au" (as calculated by the quantum calculations) to coul^{2}m/N (or coul^{2}m^{2}/J)one must multiply by 1 a.u. = 16.4877x10^{42} coul^{2}*m/N 1 a.u. = 0.148185 A^{3} 1 a.u. = 0.148185 m^{30}For example a HF/631+G(2df) calculation of carbon monoxide gives polarizability of "10" in the direction perpendicular to the molecular axis. which is 1.65x10^{40} coul^{2}m/N in fair agreement with experiment (2+0.5). Where do those terms come from? H 0.66 He 0.21 Li 12 Be 9.3 C 1.5 Ne 0.4 Na 27 Ar 1.6 K 34 Back to Top Qplus is the largest positive charge on hydrogens. Qminus is the largest negative charge.
Qplus & Qminus are known as the 'TLSER' parameters.
Ovality is a measure of how the shape of the molecule approaches a sphere or cigar. Ovality is described by the ratio of volume and area: 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. Back to Top The molecular electronegativity and hardness are generalizations of the same concept at the atomic level:
Back to Top
"LogP" methods can be selected with the LOGP= keyword; Back to Top Spartan includes a number of ways to examine solvation.
Back to Top We use the POSTSOLVENT keyword to do a energy of solvation calculation. By default Spartan 14 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 significantly solvent is added. If one wants to see the affect of solvation on the geometry, (for example for a transition state structure) the ADDSOLVENT= should be 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" pull down menu will be modified to match what was typed in. A fuller discussion of how the solvation energy is calculated can be found under solvation methods in the "Quantum Mechanical Energy FAQs". Back to Top 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 underlying basisset. Back to Top
Back to Top 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=.
Relevant references:
Back to Top The natural bond order uses similar mathematics to natural charges but is used to analyze the charge density between atoms, not centered on each atom. See the NBO keyword Natural Bond Order 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. Back to Top The MO (molecular orbital) is normalized, and the AO (atomic orbitals) are normalized. But the AOs are not orthogonal. This is why the simple algebraic norm of the coefficients is not 1.0. In order to do any quantitative work with the coefficients of the MO you will need to know the values the AO overlap integral. This is usually referred to as the overlap matrix and is represented as 'S'. Back to Top 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. Back to Top <S^{2}> is the spin operator, and it is relevant in UHF calculations. While UHF (or ROHF) is required for open shell systems and to get certain bond separation energies correctly, it suffers from the disadvantage that its wavefunctions are not (exact) eigenfunctions of the total spin operator. This is because the UHF ground state can be contaminated with functions corresponding to states of higher spin multiplicity. <S^{2}> is a measure of spin contamination and is often used as a test of how good the UHF wavefunction is. Singlet states should have a value of 0.0, doublets 0.75, and triplets 2.0. If <S^{2}> is within + .02 of these values the wavefunction is usually considered acceptable. s = (M1)/2 <S^{2}> = s*(s+1) <S^{2}> = 0, 3/4, 2, ... The <S^{2}> is printed out when the PROPPRINTLEV=1 keyword is used, and is represented in the output file as <S**2> Back to Top 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 overridden with the AVGMASS keyword, or by changing the isotope of a specific atom in the Property dialogue.. Back to Top The strength of RAMAN frequencies are calculated from the change in polarization of the molecule with respect the vibrational mode. As such, this can be much slower than just calculating standard IR intensities (dependent on the change in the dipole). It should be noted that the Intensities show in the "Output Summary" and plotted in the RAMAN graphs are scaled by the laser frequency [v_{o}] (which can be changed in the "Options" panel), plotted logarithmically and broadend with a Lorenztian. Back to Top The units of absorbance is kilometers per mol, km/mol. The justification for this unit can be surprising, so we derive this unit 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, incident over transmitted) and 'v' is the wavenumber (1/cm). Thus the unit is However, what is measured is the integrated absorption A Back to Top Full Spartan can generate a reaction path using three approaches. The simplest is via the 'energy profile' calculation, which changes specific coordinates. (See the discussion 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 single 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 selecting the IRC checkbox when performing a transition state geometry calculation. When selected, a new file will be generated that contains the reaction path. The 'Frequency' check box should also be selected. If you know you have a good transition point and a good Hessian the IRC can be run as a single point "Energy" calculation with the BE:IRC keyword. 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. Back to Top 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 the TammDancoff approximation (TDA) of time dependent density functional theory (TDDFT): 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. Back to Top 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. (Note that when you hit the "Enter" key the ESTATE keyword disappears and the n appears where the "First Excited" in the first line of the setup panel. Often you may want the first excited singlet state, which may or may not be the actual first excited state. To limit the search of possible excited states to singlets you can type in the keyword CIS_TRIPLETS=FALSE. Back to Top Assuming that the real ground state is a singlet, and the first excited state is not a triplet, these both refer to the same electronic state. A difference exists in how Spartan calculates these; excited state calculations use either CIS or TDFT methods while ground state calculations use HF or DFT methods. The later may not be as accurate, but are much faster, especially in the context of geometry optimizations. It is also possible that the first excited state is another singlet, and not a triplet. If in doubt you can do an energy calculations with the "UV/Vis Spectrum" and the INCLUDETRIPLETS keyword to look examine all the excited states. Note that the description of singlet/triplet is found in the verbose output so you will need to add the KEEPVBOSE keyword. Graphically, the intensity of the singlet to triplet will be very small. Back to Top 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 oscillator strengths 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. Back to Top Spartan's NMR package is based on the Kussman Ochsenfeld linear scaling algorithm using "gaugeincluding" atomic orbitals:
Chemical shifts are given in partpermillion (ppm) relative to the appropriate standard (nitromethane for nitrogen, fluorotrichloromethane for fluorine, and TMS for hydrogen, carbon and silicon). These relative shifts are available for HF, BP, BLYP, B3LYP, EDF1 and EDF2 models with the common 631 and 6311G basis sets. Spartan can also apply systematic corrections to the Carbon NMR depending on the nearby chemical environment. These are referred to as "corrected shifts" in Spartan. Back to Top We use modified Karplus equations to predict hydrogen coupling constants.
Back to Top The NMR calculation has it own set of SCF convergence issues. Usually the default parameters are good enough to get reasonable answers, but at times you may need to change these to get difficult systems to converge. The first thing to do is to make sure the integrals are more accurate than usual by clicking the converge checkbox in the setup panel. If you continue to have difficulty you will have to adjust some of the internal parameters to the multistep SCF logic. The most common problem is errors about "level2" iterations. By default this fails after 75 steps. This can be increased with the D_SCF_MAX_2= keyword. A list of other NMR related keywords can be found in the keyword table below. Back to Top 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's try to map the H2 molecule onto a template of the Br2 molecule with R_{Cl} set anomalously small, say 1/10 of an 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. Back to Top The score used in alignment is used in the the similarity task. The similarity task is more time consuming than alignment in that similarity will look at multiple ways of matching two molecules using different atom mappings and/or pharmacophores, and can look at multiple conformations stored in "Conformer Libraries". This score can be displayed in the resulting spreadsheet by typing Back to Top
Back to Top Below are some commonly used conversion factors: Energy: 1 au (Hartree)= me*e^4/hbar^2 = 4.3597482(26) 10^18 J * = 4.35974381(34)10^18 J (1998 CODATA) = 627.510 kcal/mol 627.5095602 kcal/mol * 627.50947093 kcal/mol (1998 CODATA [new Na]) 1 ev = 1.60217733(49) 10^19 J * 4.184 J = 1 Calorie (a constant) 1 kT (T=300K) ~ 2.495 kJ Entropy: 1 e.u. = 4.184 J/mol*K = 1 cal/mol*K Pressure: 1 kbar = 10^8 Pa = 986.923267 atm 1 atm = 101.325 k Pa (exact) * Length: 1 A = 10^10 m = 1.8897269 au (old value) = 1.889725988579 au 1 au (Bohr) = hbar^2/(me*e^2) = 0.529177249(24) A * = 0.5291772083(19) A (new CODATA 1998) Mass: 1 AMU = 1.6605402(10) 10^27 Kg (Atomic Mass Unit) = 1.66053873(13) 10^27 Kg (new CODATA 1998) Mass C12 = 12.0 AMU = 12.0 g/mol/Na 1 mn = 1.67492716(13) 10^27 Kg (Mass of neutron) 1 mp = 1.67262158(13) 10^27 Kg (Mass of proton) 1.007276470(12) AMU 1 me = 9.1034897(54) 10^31 Kg (Mass of electron) 9.10938188(72)10^31 Kg 0.5109906(15) Mev Wavenumber: 1 cm^1 = 2.9979 10^10 s^1 = 0.29979 THz 2.19474.7 cm1= 1 Hartree^1/2 Bohr^1 AMU^1/2 Wavelength: (for light = 1/Wavenumber) = h*c/Energy (for light) 1 nm = 1239.837/ev (ie. homolumo gap) = 1.9166 10^4/kJ (Na in energy) Charge: 1 au = 1 e = 1.602 10^19 C = 2.452 10^18 esu*cm Dipole moment: 1 debye(D) = 3.336e30 C*m = 0.20824 e*A 1 au = 8.479e30 C*m = 2.542e18 esu*cm = 2.542 D Polarizability: 1 au = 14.83e30 m^3 = 14.83 A^3 MomentofInertia: I cm^1 = 60.1997601/I[ AMU*bhors^2 ] I cm^1 = 16.8576522/I[ AMU*A^2 ]*In places where multiple values are listed for a given conversion, the first is the approximation used in Spartan, the second is the 'exact' value (as of 1973, 1986 or 1998). Return to Top Below are some important constants used in quantum chemistry: Speed of Light : c : 2.99792458 10^10 cm/s * (exact) Avogadro's Num. : Na : 6.0221367(36) 10^23 * Na : 6.02214199(47)10^23 (1998 CODATA) Gas Constant : R : 8.314510(70) J/K/mol * R : 8.314472(15) J/K/mol (1998 CODATA) Boltzmann const : k : 1.380658(12) 10^23 J/K * 1.3806503(24) 10^23 J/K (1998 CODATA) Planck's const. : h : 6.626075(40) 10^34 J s * 6.62606876(52)10^34 J s (1998 CODATA) finestructure : alpha: 1/137.0359895(61) 7.297352533(27) 10^3 (1998 CODATA)*In places where multiple values are listed for a given conversion the first is the approximation used in Spartan, the second is the 'exact' value (as of 1973, 1986 or 1998). Back to Top No. Data sets using the older constants have been generated
for more than 20 years. To make sure newer versions maintain
backward compatibility we continue to use the older values for
these fundamental constants and conversion factors. Even though
each new digit is an important scientific achievement,
the increased precision is well beneath the noise present in
the chemical measurements Spartan deals with.
Below is a list of all keywords which the property module understands.

 
KEEPVERBOSE  By default the verbose output file is deleted/pruned. (For many jobs this can dramatically decrease the size of .spartan files.) Instead of using this keywords, one can set the "Keep Verbose" check box in the "Preferences Panel".  
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 atomic charge calculation  
PRINTCHG PRINTCHARGE=x  Print a summary of charges and bond order. A (much) shortened version of what is printed with the MULPOP, POP, BONDORDER and NBO keywords. If x=1 only atomic charges are printed. If x=2 Mulliken bond orders are shown. If x=2 natural bond orders are shown.  
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 valences 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 "Electronic Potential at Nuclei" 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 conjunction 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.)  
POLAR  Calculate the static polarizability of the molecule. For HartreeFock and semiempirical methods this will also calculate the static hyperpolarizability. See our discussion above for more details on how to calculate polarizability for more details.  
HYPERPOLAR  Calculate the static polarizability and hyperpolarizability of the molecule. Not available for DFT methods using pure basis sets (i.e. 6311G etc.).  
POLAR=a,b,c...UNIT HYPERPOLAR=a,b,c...nnUNIT 
Calculate the polarizability at different frequencies.
There can be multiple frequencies, here represented by
'a','b', and 'c', but could be more (or fewer) comma
separated values.
UNIT should be replaced with au, nm, ev, hz
or cmInv.
For example:  
POLAR=WALK,start,end,step,UNIT 
This format of the POLAR keyword allows one to
specify a range of frequencies/energies.
This WALK format is also available for the
HYPERPOLAR keyword. As an example:  
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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. To turn "clamping" off use CLAMPTHERMO=NO  0.5 
PRINTMODE  Print thermodynamic information for each mode  
TEMPERATURE=  Change the default temperature used in the thermodynamic calculation.  298.15 K 
TEMPRANGE=start,end,step  Print thermodynamic properties for a range of temperatures.  
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 Vibrational Mode' button in the calculation dialogue panel controls.  
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.  
PRINVIBCOORDS  Print the coordinates of each vibrational mode.  
AVGMASS ISOTOPEMASS=* 
By default Spartan '14 uses the terrestrial average mass of
atoms when doing thermodynamics calculations. (Changing
the isotope of a specific atom in the property panel
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 differentiation, 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 differentiation, 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 numerical differentiation.  0.005 bohr 
DORAMAN^{2}  Calculate the Raman intensities along with the standard IR intensities.  
^{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 successively more printing. Also available are TERSE  1 
^{Back to Top} See How can I use the Intrinsic 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 yields 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 calculate the gradient for. Usually this is not entered as a keyword, but is selected by choosing 'First Excited State' in the calculation dialogue.  1 
TDA  Use the TammDancoff approximation (TDA) to then standard Time Dependent DFT (TDDFT) algorithm. (The TDA was the default method for DFT calculations prior to Spartan'14v117.) This can be up to twice as fast as the default "Full TDDFT" and produces similar, but not as precise.  
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 
CIS_TRIPLETS=FALSE^{2}  To limit the search of excited states to only singlets. Use this keyword only for excited state calculations. If this is used when doing an UV/Vis spectrum calculations this keyword will interfere with the INCLUDESINGLETS and INCLUDETRIPLETS keywords.  =TRUE 
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 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 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 molecular orbital pairs which have coefficients larger than x. This value is in hundredths so the default value of 15 implies an amplitude of 0.15. (This will go in the verbose output file, so make sure to use the KEEPVERBOSE keyword.)  15 
^{Back to Top} see Difficulty with NMR calculation  
D_SCF_MAX_2=n  The maximum number of SCFNMR steps to try before giving up. Typically, increasing this will allow difficult systems to converge.  75 
D_SCF_CONV_2=n  The tolerance/precision used in the inner (2^{nd}) part of the convergence algorithm. "n" is the decimal so the default of 2 implies 10^{2}=0.01  2 
D_SCF_MAX_1=n  Maximum number of tries in the inner NMR convergence step.  40 
D_SCF_CONV_1=n  The tolerance of the inner NMR convergence step.  0 
Notes: ^{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. 