DESCRIPTION
The program cscf carries out the iterative procedure to solve the HartreeFock equations.
This program is restricted to D2h symmetry and its subgroups and the orbital occupations are required to be integers. Thus, certain pure angular momentum states derived from partial occupation of degenerate orbitals cannot be obtained with the present codes. For example, the 2PIu (doublet PI u) state of linear ONO derived from the lowest energy linear (pi u)1 configuration may only be computed as the 2B2u (doublet B2u) or 2B3u (doublet B 3u) component of the 2PIu (doublet PI u) state, and the resulting spatial wavefunction will not have PI symmetry. In a certain sense, however, this is desirable, as the energy will be a continuous function of the bending angle. Calculating the energy of bent configurations as 2B2u (doublet B 2u) or 2B3u (doublet B 3u) and doing a pure 2PIu (doublet PI u) state at linear geometries results in a pronounced discontinuity.
For the most part, triplet states resulting from double occupation of a doubly degenerate orbital, such as the 3A2 (triplet A 2) state resulting from the (e')2 or (e")2 configurations in D3h symmetry, or the 3SIGMAg (triplet SIGMA g) state of a (pi g)2 or (pi u)2 configuration in Dinfh (D infinity h) symmetry, will have the proper spatial symetry. The singlet states resulting from these same electronic configurations are inherently multiconfiguration and, as such, are not well represented by single configuration wavefunctions.
REFERENCES
PKfile method:
 1.
 R. C. Raffenetti, Chem. Phys. Lett. 20 (1973) 335.
Molecular symmetry and closed shell HF calculations:
 1.
 M.Dupuis, and H.F.King, Int. J. Quant. Chem. 11 (1977) 613.
DIIS for closed shell:
 1.
 P. Pulay, Chem. Phys. Lett. 73 (1980) 393.
 2.
 P. Pulay, J. Comp. Chem. 3 (1982) 556.
Coupling coefficients (alpha and beta) for open shell:
 1.
 C. C. J. Roothaan, Rev. Mod. Phys. 32 (1960) 179.
Damping:
 1.
 D. R. Hartree, "The Calculation of Atomic Structures" (Wiley: New York) 1957.
 2.
 M. C. Zerner and M. Hehenberger, Chem. Phys. Lett. 62 (1979) 550.
Level shifting:
 1.

V. R. Saunders and I. H. Hillier, Int. J. Quant. Chem. 7 (1973)
699.
CONVERGING CSCF
For difficult open shell cases, it is recommended that an appropriate closed shell calculation be run first (add or remove an extra electron) and that this SCF vector then be used as a guess for the desired open shell wavefunction. For TCSCF cases, it is always wise to run a closed shell (or perhaps the appropriate triplet) SCF first and then use this as a guess for the TCSCF.
For open shell systems, a level shift value of 0.5 to 3.0 is recommended. Start with a high value (2.0  3.0) for the first SCF calculation and then reduce it (to 0.5  1.0) for subsequent runs which use a converged SCF vector as the starting point.
It is extremely important to note that this version of the code no longer supports OPENTYPE. One must use the new keywords REFERENCE and MULTP to specify the type of SCF needed.
INPUT FORMAT
The cscf program searches through the default keyword path (first SCF and then DEFAULT) for the following keywords:
 LABEL = string

This is a character string to be included in the output. This string is not
used by the program.
There is no default.
 WFN = string

This is the type of wavefunction which is ultimately desired.
The default is
SCF.
 OPENTYPE is no longer supported

 REFERENCE = string

This specifies the type of SCF calculation
one wants to do. It can be one of
RHF
(for a closed shell singlet),
ROHF
(for a restricted open shell calculation),
UHF
(for an unrestricted open shell calculation),
TWOCON
(for a two configuration singlet), or
SPECIAL.
If SPECIAL is given, then
alpha
and
beta
coupling coefficients must be given with the
ALPHA
and
BETA
keywords.
The default is
RHF.
 MULTP= integer

Specifies the multiplicity of the molecule. Default is singlet.
 CHARGE= integer

Specifies the charge of the molecule. Defauly is 0.
 DOCC = integer_vector

This gives the number of doubly occupied orbitals in each
irreducible representation. There is no default. If this
is not given, CSCF will attempt to guess at the occupations
using the core hamiltonian.
 SOCC = integer_vector

This gives the number of singly occupied orbitals in each
irreducible representation. There is no default.
 DERTYPE = string

This specifies the order of derivative that is to eventually be done.
It is used by the
scf
program to determine if certain files are to be written and it is
also used to determine the default convergence of the wavefunction.
The default is
FIRST.
 MAXITER = integer

This gives the maximum number of iterations.
The default is 40.
 CONVERGENCE = integer

This specifies how tightly the wavefunction will be converged.
Convergence is determined by comparing the RMS change in the density
matrix ("delta P") to the given value. The convergence criterion is
10**(integer).
The default is 7
if both DERTYPE = NONE and WFN = SCF are given
and 10 otherwise.
 LEVELSHIFT = real

This specifies the level shift. The default is 1.
 DIRECT = boolean

Specifies whether to do the SCF calculation with
an integral direct technique. The default is false.
 PRINT_MOS = boolean

Specifies whether to print the molecular orbitals or not.
The default is false.
There are also a large number of less commonly used input parameters. If you do not understand what the following options mean, then make sure that they do not appear in your input. The defaults will work in the overwhelming majority of cases. These are specified with the following keywords:
 DELETE_INTS = boolean

Integrals files
will be erased if WFN = SCF and DERTYPE = FIRST
or DERTYPE = NONE.
If you wish to keep
integrals files then set DELETE_INTS = false. The default is true.
 REORDER = string

The parameter controls reordering of molecular orbitals.
If set to BEFORE then the guess orbitals from checkpoint file
will be reordered. If set to AFTER, converged orbitals
will be reordered before being written to the checkpoint file.
In either case MOORDER parameter must be given to specify the
reordering map. The default is not to reorder orbitals.
 MOORDER = integer_vector

This specifies a molecular orbital reordering vector. It will only
be used if REORDER is set. This vector maps every orbital
to its new index, e.g. MOORDER = (0 2 1) specifies that
after reordering orbitals 1 and 2 will be swapped. The rank of this
vector is the same as the number of MOs. The indices are in Pitzer order
(ordered by symmetry, then by energy within each symmetry block), base0.
CSCF will likely fail if the given MOORDER mixes orbitals from
different irreps. There is no default.
 ALPHA = real_vector

If OPENTYPE = SPECIAL, then this parameter gives the
alpha
coupling coefficients. The number of elements in this vector is
MM(MM+1)/2, where MM is the number of
irreducible representations containing singly
occupied molecular orbitals.
There is no default.
 BETA = real_vector

If OPENTYPE = SPECIAL, then this parameter gives the
beta
coupling coefficients. The number of elements in this vector is
MM(MM+1)/2, where MM is the number of
irreducible representations containing singly
occupied molecular orbitals.
There is no default.
 GUESS = string

This option determines the type of initial guess at the eigenvector
CSCF will use. The only valid option at the moment are : (1) GUESS = CORE,
which causes it to use core Hamiltonian eigenvector to start the calculation;
(2) GUESS = AUTO which results in an attempt to use the MO vector
in the checkpoint file, or resorts to core guess if there is no eigenvector
in that file. The default if AUTO.
 IPRINT = integer

This is a print option.
The default is 0.
 MO_OUT = boolean

Prints out the orbitals with symmetry and occupations
at the end of the calculation. Default is true.
 ROTATE = boolean

The molecular orbitals will not be rotated if this is false.
The rotation only affects the virtual orbitals for open shell systems.
This parameter must be true for correlated gradients and it must be
false for second and higher derivatives.
The default is false if WFN = SCF
and true otherwise.
 CHECK_ROT = boolean

Check the molecular orbital rotation described above to ensure that
no columns of the SCF eigenvector matrix are swapped by the rotation.
Has no effect if ROTATE = false. The default is true.
 CHECK_MO_ORTHOGONALITY = boolean

Check if the molecular orbitals are orthonormal. Useful for debugging only.
The default is false.
 DIIS = boolean

This determines whether diis will be used. The default is
true.
 DIISSTART = integer

This gives the first iteration for which DIIS will be used.
The default is 0.
 NDIIS = integer

This gives the number of error matrices to use in the diis
procedure. The default is 6 for closed shell, 4 for open
shell, and 3 for tcscf.
 DIISDAMP = real

This gives the damping factor for the diis procedure. The
default is 0.0 for closed shell, 0.02 for open shell, and
0.01 for tcscf.
 INCR = real

This is used in tcscf to determine how often the ci
coefficients are recalculated. A small number (~0.25)
will cause them to be recalculated nearly every scf
iteration. The default is 0.25.
 DYN_ACC = boolean

When performing direct scf this specifies whether dynamic integral
accuracy cutoffs will be used. Default is true (use dynamic cutoffs).
Initial iterations are performed with integrals accurate to six digits.
After density is converged to 10^5 or 30 iterations are completed,
full integral accuracy is used. If scf convergence problems are experienced
disabling dynamic cutoffs by setting this variable to false might help.
 ORTHOG_ONLY = boolean

Sometimes in CASSCF or other nonHF/KS schemes for orbital optimization,
it is useful to reorthogonalize MO's from other geometries for the current
geometry so they can be used as an initial guess for the new MO's. This
can be performed by running CSCF with ORTHOG_ONLY = true. After
the orbitals are orthogonalized, the program will quit without performing
an SCF computation. This keyword will be ignored if there are no
previous orbitals in the checkpoint file. Defaults to true if
WFN = DETCAS.