Main /
## List Of Keywords In Alphabetical OrderA B C D E F G H I J K L M N O P Q R S T U V W X Y Z specifies the way the {$\langle ab||cd\rangle$} molecular
orbital integrals are handled in post-MP2 calculations.
specifies the active orbitals used in a TCSCF calculation and has to be used in combination with the keyword
specifies treatment of anharmonc effects by calculating
cubic and/or quartic force fields.
specifies which algorithm is used for
specifies the number of points used for the numerical differentiation in the computation of cubic and quartic force constants based on analytically evaluated Hessians. 1 refers to the
standard two-point formula, 2 refers to the four-point formula, etc.
Default:
specifies whether the anharmonic force field is calculated using analytic gradients
(
Controls the stepsize used in anharmonic force
field calculations. The value is specified in reduced normal coordinates,
which are dimensionless. The actual stepsize used in the calculation
is 10$^6$ the value specified(as an integer) in the ZMAT file.
Specifies whether nonabelian symmetry is to be
exploited in determining displacements for
Can be used to control the algorithm used by CFOUR when terms involving {$\langle ab||cd\rangle$} molecular orbital integrals are calculated in the atomic orbital basis (see keyword ABCDTYPE above).
specifies the AO basis used in the calculation. One can either specify a basis
known to
Default:
experimental use
specifies the convergence criterion in Brueckner based CC calculations. The calculation
is considered to be converged when the absolute value of largest single excitation amplitudes
falls below 10$^N$, where
specifies whether Brueckner orbitals are to be determined for the specified CC method.
experimental use defines the level of calculation to be performed. Available are:
The number of records held in the i/o cache used by the post-SCF programs. The maximum number of records which can be held is 100.\\ Default :
experimental use
specifies the convergence criterion for the CC amplitude equations. The amplitudes are
considered to be converged when the maximum of all (absolute) changes in the amplitudes is less
than 10$^N$, where $N$ is the value associated with the keyword.
specifies the maximum number of expansion vectors used in the iterative subspace to enhance convergence
in the solution of the CC equations.
specifies the type of convergence acceleration used to solve the CC equations.
specifies the maximum number of iterations in solving the CC amplitude equations.
specifies which CC program is used. The available options are Note: Using the option
specifies the molecular charge.
specifies whether Cholesky decomposition of two-electron integrals is used (
specifies the convergence threshold (as {$10^{-N}$} for CIS calculations.
experimental use
signifies that one or more "continuum" orbitals should be added to the calculation.
specifies the contraction scheme used by the integral and integral derivative program.
specifies convergence criterion for geometry optimization. Job terminates when RMS gradient is below {$10^{-N}$} Hartree/bohr, where $N$ is the value specified by CONVERGENCE. (Value must be specified as an integer).
specifies the type of coordinates used in the input file
specifies the core orbitals used in a TCSCF calculation and has to be used in combination with the keyword
specifies the convergence criterion for the iterative solution of the CPHF and Z-vector equations. The solutions are considered
to be converged when the residual norm of the error vector falls below 10$^N$.
specifies the maximum number of cycles allowed for the solution of the CPHF- and/or Z-vector equations.
specifies whether or not Hessian matrix is transformed (nonlinearly) to curvilinear internal coordinates. A value of 0 (or OFF) turns the transformation off if the analytic force constants are not available, while it is always performed if CURVILINEAR=1 (or ON). Values higher than 1 (or NO) unconditionally turn the transformation off. specifies whether the diagonal Born-Oppenheimer correction (DBOC) to the energy is evaluated (
specifies whether the Dipole Coupling Tensor (DCT) is calculated (
specifies whether or not energy derivatives are
to be calculated and if so whether first or second derivatives are computed.
specifies whether orbital-relaxed (
experimental use
experimental use
specifies which molecular orbitals will be dropped from
the post-SCF calculation. The orbitals are numbered in ascending order
from the most stable (negative energy) to the most unstable (largest
positive energy). Individual orbitals must be separated with a dash,
while x>y means orbitals x through y inclusive. For example,
the string 1>10-55-58>64, would result in
orbitals 1,2,3,4,5,6,7,8,9,10,55,58,59,60,61,62,63
and 64 being dropped. For UHF calculations,
the appropriate orbitals are deleted for both spin cases. No dropped
virtual MOs are currently allowed for gradient or property calculations. experimental use
experimental use
specifies whether effective core potentials (pseudopotentials) are used (
specifies which eigenvector of the totally symmetric
part of the block-factored Hessian is to be followed
experimental use,
specifies the threshold used in converging CC-LR/EOM-CC calculations.
The iterative diagonalization is continued until the RMS residual falls below {$10^{-N}$}
with
experimental use
experimental use
controls whether non-iterative triples corrections are applied after various types of EOM-CCSD calculation. Works with EOMIP, might work with EOMEE, certainly doesn't work with EOMEA. Use with great caution, preferably after having a few drinks. Options are OFF and ON.
for experimental use only. Selects the iterative diagonalization algorithm for the EOMEE calculations.
If set to
experimental use.
experimental use.
experimental use.
The maximum number of expansion vectors used in the solution of EOMCC equations.
This keyword applies only to EOM-CC calculations and specifies whether any excited or ionized state one-electron properties are to be calculated. Proper use of this keyword requires a relatively advanced knowledge of quantum chemistry and the available options are discussed here. The options are : OFF (=0) [no properties or transition moments are calculated]; EXPECTATION (=1) [transition moments and dipole strengths are calculated along with selected one-electron properties which are evaluated as expectation values]; UNRELAXED (=2) [selected one-electron properties are calculated in an approximation that neglects relaxation of molecular orbitals]; RESPONSE (=3) [selected one-electron properties are calculated as analytic first derivatives of the energy]. Except for EOMCC calculations on two-electron systems (which are exact), properties obtained by the three approaches will not be equivalent. The default value for this keyword is slightly complicated. For TDA calculations, the default is EXPECTATION since the evaluation of transition moments involves only a negligible amount of additional computation relative to the evaluation of the excitation energies. For EOMCC, the default is OFF since evaluation of any transition moments or properties requires approximately twice the computational time. Transition moments and dipole strengths are evaluated by default for all values of ESTATE_PROP other than OFF.
specifies the number of excited states which are to
be determined in each irreducible representation of the computational
subgroup. The program attempts to find all of the lowest roots, but this
is not guaranteed because the eigenvalue problem is not solved by direct
matrix diagonalization, but rather by an iterative (modified Davidson)
algorithm. For excited state gradient calculations, only one
root (clearly) is used. In such a case, one and only one non-zero entry in
the string can be used, and this value is usually set to one (i.e.
ESTATE_SYM=0/1/0/0). (However sometimes one wants to calculate the gradient for,
say, the second root of a given symmetry, and in such a case, one could use
ESTATE_SYM=0/2/0/0. What happens is that both roots are calculated, but only the
second one is used in the subsequent density matrix and gradient calculation.)
The format used for this keyword is identical to that used in the OCCUPATION keyword, i.e. in the order A
specifies whether just the excitation energies (
tells the program, in the course of a geometry optimization, to calculate the Hessian explicitly every N cycles.
specifies in CC calculations using
specifies the type of EOM-CC/LR-CC treatment to be performed. Available options are
allows the use of external pointcharges. Available options are
Specifies the strength of a Fermi-Contact pertubation as required for finite-field calculations of spin densities and the FC contributions to indirect spin-spin coupling constants. The value must be specified as an integer and the FC strength used by the program will be the value of the keyword $x 10^{-6}$. The atom for which the FC perturbation is switched on is specified in the ZMAT file after the CFOUR command line and potential basis set input, as follows %spin density N with N as the number of atom (in (X5,I3) format) in the order they are written by JODA to the MOL file. Be aware that for some atoms, the calculation has to be run in lower symmetry or even without symmetry.
specifies the algorithm used to compute the harmonic force constants in finite-difference
calculations.
requests that only vibrational
frequencies of certain symmetry types are evaluated in a
specifies whether or not rotational degrees of freedoms are projected out from the symmetry-adapted coordinates
in a finite difference calculations.
specifies the step length in mass-weighted coordinates (in 10**(-4) amu**0.5 bohr) used in generating
the force constant matrix by finite difference of Cartesian gradients.
In finite difference calculations using the FINDIF option, this keyword specifies the point group to be used in generating the symmetry-adapted vibrational coordinates. FULL (= 0) specifies the full molecular point group, COMP (= 1) specifies the Abelian subgroup used in the electronic structure calculation.
This specifies the physical length (in integer words) of the records used in the word-addressable direct access files used by CFOUR. This value should always be chosen as a multiple of 512 bytes, as your local system manager certainly understands.
This option allows the splitting of files. Input is required in the form FILE_STRIPE=N1/N2/N43/N4/N5, where N1, N2, N3, N4, and N5 specify the number of files in which MOINTS, GAMLAM, MOABCD, DERINT, and DERGAM are splitted, respectively.
specifies the field strength for a perturbation (defined
within a %perturbation section). The value must be given as an integer, and the field strength used by the program will be then the value of the keyword {$x10**(-6)$}.
This option is used to control the algorithm used for construction of the Fock matrix in SCF calculations.
experimental use.
specifies whether in the correlation treatment all electron (
specifies whether in the correlation treatment all virtual orbitals ( Used to control the handling and storage of two-particle density matrix elements with four virtual indices $\Gamma(abcd)$. DISK (=0) directs the program to calculate and store all elements of $\Gamma(abcd)$, while DIRECT (=1) tells the program to use alternative algorithms in which $\Gamma(abcd)$ is calculated and used ``on the fly''. Note that this option might be not available for all type of calculations.
see GAMMA_ABCD.
This keyword applies only to Hydrogen and Helium atoms and
specifies the number of contracted Gaussian functions per shell. There is
usually
This keyword performs the same function as
This keyword performs the same function as
This keyword performs the same function as
specifies the convergence criterion for geometry optimization.
The optimization terminates when the RMS gradient is below {$10^{-N}$} Hartree/bohr, where
N is the specified value.
specifies largest step (in millbohr) which is allowed in geometry optimizations.
specifies the used geometry optimization methods. The following values are
permitted:
Specifies convergence criterion for geometry optimization. Job terminates when RMS gradient is below {$10^{-N}$} Hartree/bohr, where $N$ is the value specified by CONVERGENCE.
specifies whether gauge-including atomic orbitals (GIAOs, London atomic orbitals) are used (
experimental use.
Keyword used to control type of grid calculation (see later section in this manual). Options are OFF (= 0), no grid calculation; CARTESIAN (= 1), steps are in Cartesian coordinates (which must be run with COORD=CARTESIAN); INTERNAL (= 2), steps are in Z-matrix internal coordinates; QUADRATURE (= 3) steps are chosen for an integration based on Gauss-Hermite quadrature.
experimental use.
Where the initial SCF eigenvectors are read from. MOREAD means to read from the disk (the `` JOBARC" file) and CORE means to use a core Hamiltonian initial guess. If MOREAD is chosen but no disk file is present, the core Hamiltonian is used. This keyword determines which action is taken by the linear response program. ON (= 1) the full effective Hamiltonian is calculated and written to disk; OFF (= 0) the ``lambda'' linear response equations are solved.
experimental use.
control analysis of the stability of RHF, ROHF and UHF wavefunctions,
as well as a possible search for a lower SCF solution. There are
three possible options for this keyword.
experimental use. This keyword can be used to significantly reduce disk i/o, and should be implemented very soon. The following options are available: OFF (= 0), no special algorithms are used (the default case); ALL (=1) all quantities except the $\langle ab\vert\vert cd\rangle$ molecular integral lists are held in core; PARTIAL (= 2), the T2 and T1 vectors are held in core throughout the calculation; (=4) all quantities except the $\langle ab\vert\vert cd\rangle$ and $\langle ab\vert\vert ci\rangle$ integrals are held in core; (=5) $\langle ij\vert\vert kl\rangle$ and $\langle ij\vert\vert ka\rangle$ and two-index quantities are held in core; (=6) all direct access files (MOINTS, GAMLAM, etc.) are held in core. At present, these options have been implemented only in the energy code (xvcc) and the excitation energy code (xvee).
specifies whether an input for
This keyword defines what type of integral input will be written by JODA. VMOL (=1) or MINT (=0) have to be used with the programs of CFOUR.
This keyword is relevant for CC_PROGRAM=SACC and defines the symmetry (irreducible representation) of the singly occupied orbital in the reference state. For the closed-shell case, IRPSING=0. For SACC calculations involving open-shell doublet states, one could either use an ROHF reference state (REF=ROHF, MULT=2) or the RHF determinant of a closed-shell state obtained by adding an extra electron into the singly occupied orbital (REF=RHF, MULT=1). For both choices of the reference for a doublet state, IRPSING should be set to a nonzero value, viz., to the symmetry of the singly occupied orbital. Controls amount of debug printing performed by Joda. The higher the number, the more information is printed. Values of 25 or higher generally do not produce anything of interest to the general user. Do not set JODA_PRINT to 999 as this will cause the core vector to be dumped to disk. Dumps the keywords and their numerical designations.
Default: Convergence threshold for linear equations controlled by LINEQ_TYPE. Equations are iterated until smallest residual falls below {$10^{-N}$}, where N is the value associated with this keyword.
Maximum subspace dimension for linear equation solutions.
Determines the algorithm used to solve linear equations ($\Lambda$ and derivative $T$ and $\Lambda$). POPLE (=0) uses Pople's method of successively orthogonalized basis vectors, while DIIS (=1) uses Pulay's DIIS method. The latter offers the practical advantage of requiring much less disk space, although it is not guaranteed to converge. Moreover, POPLE has not been tested for some time and should definitely be checked!\\
Default:
The maximum number of iterations in all linear CC equations.
The tolerance for basis set linear dependence. The basis set is considered linearly dependent and eigenvectors of the overlap matrix are neglected if the associated eigenvalues are less than {10$^{-N}$}.\\
Default:
This keyword is used by the SCF program to determine if the orbital occupancy (by symmetry block) is allowed to change in the course of the calculation. ON (= 1) locks the occupation to that set by the keyword OCCUPATION [or the initial guess if OCCUPATION is omitted]; OFF (= 0) permits the occupation to change.
This keyword specifies the procedure used to determine localized orbitals (if requested) options are here PIPEK-MEZEY (=0) and FOSTER-BOYS (=1).
This keyword defines the convergence criterion for the orbital localization procedure. It sets the threshold for the maximum angle for orbital rotations to {$10^{-N}$} with N as the value specified.
This keyword specifies the procedure used for the local MP2 treatment(if requrested). Specifies largest step (in millibohr) which is allowed in geometry optimizations.
specifies the amount of core memory used in
specifies the units in which the amount of requested core memory is given. Possible choices are
specifies the geometry optimization strategy. Four values are permitted: 0 (or NR) -- Straightforward Newton-Raphson search for minimum; 1 (or RFA) -- Rational Function Approximation search for minimum (this method can be used to find minima when the initial structure is in a region where the Hessian index is nonzero); 2 (or TS) Cerjan-Miller eigenvector following search for a transition state (can be started in a region where the Hessian index is not equal to unity); 3 (or MANR) -- Morse-adjusted Newton-Raphson search for minimum (very efficient minimization scheme, particularly if the Hessian is available); 4 is currently unavailable; 5 (or SINGLE_POINT) is a single point calculation.
specifies the type of MRCC calculation.
specifies the spin multiplicity. Calculation of non-adiabatic coupling. In case of
specifies what to do if negative eigenvalues
are encountered in the totally symmetric Hessian during an
all components of spherical AO’s are normalized to 1. This feature can help with numerical convergence issues if AO integrals are involved. Currently only working for single-point energy calculations.
specifies whether the reference function used in the correlation energy calculation satisfies the (spin-orbital) HF equations or not.
Usually there is no need to set this parameter (
specifies how many t amplitudes will be printed for each spin case and excitation level. =N The largest N amplitudes for each spin case and excitation level will be printed. (Default : 15).
specifies which model is used for the nuclei. Defaults is the point-nucleus model ( specifies the orbital occupancy
of the reference function in terms of the occupation numbers of the orbitals and
their irreducible representations. The occupancy is specified by
either
specifies which kind of open-shell CC treatment is
employed. The default is a spin-orbital CC treatment (
specifies the maximum allowed number of geometry optimization cycles.
specifies the type of molecular orbitals used in post-HF calculations. experimental use.
experimental use.
experimental use.
specifies the type of perturbed orbitals used in energy derivative calculations.
specifies whether pair natural orbitals (PNOs) are used in a local MP2 treament. The options are OFF (=1) and ON (=2).
specifies the cutoff for the selection of PNOs are used in a local MP2 treament.\\
Default:
specifies either single (=1, or SINGLE) or double (=2, DOUBLE) sided numerical differentiation in the finite difference evaluation of the Hessian. Two-sided numerical differentiation is considerably more accurate than the single-sided method and its use is strongly recommended for production work.
controls the amount of printing in the energy and energy derivative calculation programs. Using a value of 1 will produce a modest amount of additional output over the default value of 0, which includes some useful information such as SCF eigenvectors, Fock matrix elements, etc.
specifies whether and which molecular property is calculated.
allows storage of property integrals computed in
??? Specify which algorithm to use for QCSCF. Options are "FLM" (0) for the Flectcher-Levenberg-Marquardt optimization, which is the default, and "AH" (1) for a more standard Augmented Hessian optimization. AH is more efficient than FLM, however, FLM is guaranteed to converge.
Specify the maximum number of cycles in a QCSCF calculations.
Specify the maximum number of standard SCF cycles before the QCSCF optimizazion. This preliminary iterations are used to determine the occupation number (which should therefore always be double checked, or provided from input).
Specify whether to add a random perturbation to the MO rotation gradient at the beginning of the second-order optimization. This can be useful to break an unwanted symmetry and is only relevant for DQCSCF.
Trust radius for the second-order SCF optimization. Integer, the actual trust radius is QC_RTRUST/1000. The default (0) corresponds to a trust radius of 0.66 for RHF and ROHF (not part of the public release) and 0.25 for UHF. The defaults are reasonable for most cases, consider reducing them only for very, very hard convergence problems.
Specify the convergence threshold for the preliminary SCF iterations before switching to quadratically convergent ones. Default is -1, as 10^(-(-1)) for the RMS variation of the density matrix and 10^0 for the Max variation.
The presence of this keyword specifies that a QRHF based CC calculation, or alternatively, an SCF calculation that uses the QRHFGUES option, is to be performed.
If this keyword is set to
No longer used; antiquated way of specifying QRHF occupation changes.
By default, in QRHF calculations, electrons are removed from the highest occupied orbital in a symmetry block (symmetry block HOMO), while electrons are added to the lowest unoccupied orbital within a symmetry block (symmetry block LUMO). The purpose of the QRHF_ORBITAL keyword is to allow additional flexibility in choosing which orbitals will have their occupation numbers altered. The value of this keyword gives the offset with respect to the default orbital for the orbital which will be depopulated (or populated) in QRHF-CC calculations. For calculations involving more than one removal or addition of electrons, values are separated by commas and correspond to the QRHF_GENERAL input on a one-to-one basis. For example, specifying QRHF_GENERAL=2/-4,QRHF_ORBITAL=3/2 means that an electron will be added to the third lowest virtual in symmetry block 2 and another will be removed from the second highest occupied orbital in symmetry block 4. Examples given later in this manual further illustrate the QRHF input options and may help to clarify any confusion resulting from this documentation.\\
Default:
No longer used; antiquated way of specifying QRHF occupation changes.
specifies the spin of the electrons modified
by the
specifies whether Raman intensities are calculated
with orbital relaxation with respect to the electric
field perturbation (
specifies whether or not relaxed density natural orbitals are to be computed. This option only has meaning for a correlated calculation. =0 Do not compute, =1 compute.\\
Default:
specifies the type of SCF calculation to be performed.
specifies the treatment of relativistic effects. The default is a non-relativistic treatment (
specifies whether the relaxed density matrix is computed for correlated wave functions. OFF (= 0) The relaxed density will not be computed, ON (= 1) it will be computed. (Default : 0).
this option can be used to convert an analytically calculated gradient vector to a particular normal coordinate representation. A useful application is to calculate the gradient of an electronically excited state in the normal coordinate representation of the ground electronic state, as this provides a first approximation to resonance Raman intensities (hence the name of the keyword). Calculations that use the RESRAMAN option require the externally supplied force constant matrix FCMFINAL, which is written to disk during the course of both analytic and finite-difference vibrational frequency calculations. No such transformation is performed if OFF (=0); while ON (=1) directs the program to evaluate the gradient and transform it to the chosen set of normal coordinates. A warning message is printed if the force constant matrix is unavailable.\\
Default:
experimental use.
offers the possibilty to restart a CC calculation which stopped for various reasons, e.g. time limit, in the correlation part. However, note that a restart which is specified by ON (= 1) needs the following files of the previous unfinished calculation: JOBARC, JAINDX, MOINTS, and MOABCD.
specifies which eigenvector of the orbital
rotation Hessian is to be used to rotate the original SCF orbitals. By
default, it will use that associated with the lowest eigenvalue of the
totally symmetric part of the block-factored Hessian, as this choice often
leads to the lowest energy SCF solution. For RHF stability checks, only
those instabilities which correspond to RHF solutions will be considered.
It is important to understand that following non-symmetric eigenvectors
lowers the symmetry of the wavefunction and that following
RHF --> UHF stabilities leads to a UHF solution.
To converge the SCF roots associated with such instabilities, one must
run the calculation in reduced symmetry and as a closed-shell UHF
case, respectively. relevant if CC_PROGRAM=SACC and specifies the type of the spin-adapted open-shell CC ansatz for the doublet case.
relevant if CC_PROGRAM=SACC and defines the type or the stage of the SACC calculation. The SACC_CALC=DENSITY run for a doublet state: - If REF=ROHF and MULT=2 are used, the QRHF_G, QRHF_O, and QRHF_S keywords must be specified in the input as if an extra electron is being added to the singly occupied orbital in the ROHF reference. For example, for the
^{2}A_{1}state of H_{2}O^{+}with an ROHF reference corresponding to OCCUPATION=3-1-1-0/2-1-1-0, one would specify QRHF_G=1, QRHF_O=1, QRHF_S=2. This means that an extra electron will be added to the highest energy occupied orbital of symmetry 1 and spin type 2 (i.e., beta spin orbital). These keywords will be used for defining a closed-shell vacuum state within the program, which forms the foundation for the open-shell SACC methods. Note: QRHFGUES should be set to 'OFF'. - If REF=RHF and MULT=1 are used, i.e., a closed-shell RHF reference state with an extra electron than the target doublet state, there is no need for the QRHF keywords in the input.
The SACC_CALC=PROPERTIES run for a doublet state: - The QRHF keywords should be omitted from the input irrespective of whether ROHF or RHF reference is employed.
For closed-shell molecules, the QRHF keywords are to be omitted altogether.
relevant if CC_PROGRAM=SACC and specifies the type of orbitals to be used for SACC calculations.
relevant for the case CC_PROGRAM=SACC and specifies whether orbital-relaxed (
tells CFOUR whether to delete large files (AO integrals and MOINTS file for now) when they are no longer needed. OFF (= 0) They will not be saved, ON (= 1) they will be saved.
controls whether step scaling is based on the absolute step length (1-norm) (=0 or MAG(S)) or the largest individual step in the internal coordinate space (=1 or MAX(S)).\\
Default:
specifies the convergence criterion for the HF-SCF equations.
Equations are considered converged when the maximum change in
density matrix elements is less than 10$^{-N}$.
controls the damping (in the first iterations
(specified by
specifies the number (
specifies the first iteration in which the DIIS
convergence acceleration procedure is applied.
specifies whether or not the DIIS extrapolation
is used to accelerate convergence of the SCF
procedure.
specifies the maximum number of SCF iterations.
This keyword is no longer in use.
Specifies whether to use the standard or the quadratically convergent SCF code. Options are "SCF" (0), "QCSCF" (1), and "DQCSCF" (2). "DQCSCF" is not part of the public release. Default : """0"""
specifies the strength of a spin-dipole pertubation as required for finite-field calculations of the SD contributions to indirect spin-spin coupling constants. The value must be specified as an integer and the SD strength used by the program will be the value of the keyword $x 10^{-6}$. (Default : 0, currently not implemented)
Default : Perturbative treatment of spin-orbit splittings in dublett-pi states via multireference coupled-cluster theory.
specifies whether spherical harmonic
(5d, 7f, 9g, etc.) or Cartesian (6d, 10f, 15g, etc.) basis functions
are to be used.
controls whether excitation energy calculations allow for a ``spin flip'' which changes the $M_s$ quantum number. Such calculations have some advantages for biradicals and are currently implemented (together with gradients) for CIS and CIS(D) calculations. Options are OFF and ON.\\ Default :
Experimental Use!
experimental use.
specifies whether nuclear spin-rotation tensors are computed within a NMR chemical
shift calculation (
specifies an Abelian subgroup to be used in a calculation. Acceptable arguments are
is a somewhat complicated keyword to use. Allowed values are 0, 1, and 2, which specify the $x$,$y$, and $z$ axes, respectively. The meaning of the keyword is best described by example : Suppose one is running a calculation on water, and wishes to run it in the $C_s$ point group with the ``special
in principle can be used to force the SCF to converge a solution for which the density matrix transforms as the totally symmetric representation of the point group (i.e. no broken symmetry solutions). The code seems to work in most cases, but has currently been implemented for point groups with E type representation and not for those with triply-, quadruply- or pentuply-degenerate representations. Extending the code to those cases is probably straightforward, and the reader is encouraged to do so if (s)he is so inclined. SYM_CHECK=0 ``forces'' the high-symmetry solution; SYM_CHECK=OVERRIDE (= 1) doesn't. The latter is the default.
specifies what subgroup of the full point group is
to be used in the energy and/or gradient calculation
(The computational point group).
specifies whether the T3 amplitudes are included (
specifies whether the T4 amplitudes are included (
specifies how often the largest t amplitudes are to be printed. =0 Amplitudes are printed at the beginning and end of the run, =1 Amplitudes are printed every iteration, =2 Amplitudes are printed every other iteration, etc. (Default : 5).
experimental use
(currently not available)
specifies whether to calculate finite-temperature thermodynamic
corrections after a frequency calculation.
specifies the threshold to be used in Cholesky decomposition of the two-electron integrals; Cholesky vectors are considered until the
residual is lower than 10$^{-N}$.
experimental use
specifies whether or not translational invariance is exploited in geometrical derivative calculations.
specifies whether in a correlated NMR chemical shift calculations all perturbations
are treated at once or sequentially. Available option are specifies the threshold value
(given as an integer)
for the treatment of CPHF coefficients in second derivative
calculations using perturbed canonical orbitals. If a CPHF coefficient
is above the threshold, the corresponding orbital rotation is treated
(at the expense of additional CPU cost) using the standard non-canonical
procedures, while orbital pairs corresponding to CPHF coefficients below
the threshold are treated using perturbed canonical representation.
specifies the units used for molecular geometry input.
experimental use
specifies whether or not the Hessian update is carried out.
experimental use
experimental use
specifies whether (harmonic) vibrational frequencies are calculated or not.
If the default
This keyword specifies whether virtual natural orbitals are to be used (USE) or not (OFF). (Default : OFF)
This keyword defines what type of integral transformation is to be performed in the program VTRAN. FULL/PARTIAL (=0) allows the transformation program to choose the appropriate type of transformation, while FULL (=1) requires a full integral transformation and PARTIAL (=2) means an MBPT(2) Specific transformation where the (ab $\vert$ cd) integrals are not formed. functions. (Default : FULL/PARTIAL) specifies the X-component of an external electric
field. The value must be specified as an integer and the field
used by the program will be the value of the keyword {$x10**(-6)$}.
This allows field strengths {$|\varepsilon| > 10^{-6}$} to be used.
The tolerance for storing transformed integrals. Integrals less than $10^{-N}$ are neglected and not stored on disk. (Default: 11). specifies the Y-component of an external electric
field. The value must be specified as an integer and the field
used by the program will be the value of the keyword {$x10**(-6)$}.
This allows field strengths {$|\varepsilon| > 10^{-6}$} to be used. specifies the Z-component of an external electric
field. The value must be specified as an integer and the field
used by the program will be the value of the keyword {$x10**(-6)$}.
This allows field strengths {$\varepsilon| > 10^{-6}$} to be used. |

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CFOUR is partially supported by the U.S. National Science Foundation.