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$CIGEN group (required if CITYP=GENCI)
This group describes the determinants to be used in a
MCSCF or CI wavefunction:
a) For full CI calculations (ALDET) the $DET/$CIDET
will generate a full list of determinants. If the CI is
part of an MCSCF, this means the MCSCF is of the FORS type
(which is also known as CASSCF).
b) For Occupation Restricted Multiple Active Space
(ORMAS) CI, the input in $ORMAS will partition the active
orbitals defined here into separate spaces, that is,
provide both $DET/$CIDET and $ORMAS.
c) For Full Second Order CI, provide $CIDET and $SODET
inputs.
d) For a general CI (meaning user specified space orbital
products) provide $DET/$CIDET plus $GEN/$CIGEN and most
likely $GCILST (according to the keyword GLIST).
In the above, group names for MCSCF/CI jobs are separated
by a slash.
Determinants contain several spin states, in contrast
to configuration state functions. The Sz quantum number
of each determinant is the same, but the Hamiltonian
eigenvectors will have various spins S=Sz, Sz+1, Sz+2, ...
so NSTATE may need to account for states of higher spin
symmetry. In Abelian groups, you can specify the exact
spatial symmetry you desire.
GLIST = general determinant list option
The keyword GLIST must not be given in a $DET or
$CIDET input group! These both generate full
determinant lists, automatically.
= INPUT means $GCILST input will be read.
= EXTRNL means the list will be read from a disk
file GCILIST generated in an earlier run.
= SACAS requests generation of sevaral CAS spaces
of different space symmetries, specified by
the input IRREPS. This option is intended
for state averaged calculations for cases
of high symmetry, where degenerate irreps
of the true group may fall into different
irreps of the Abelian subgroup used.
* * * The next four define the orbital spaces * * *
There is no default for NCORE, NACT, and NELS:
NCORE = total number of orbitals doubly occupied in all
determinants.
NACT = total number of active orbitals.
NELS = total number of active electrons.
SZ = azimuthal spin quantum number for each of the
determinants, two times SZ is therefore the
number of excess alpha spins in each determinant.
The default is SZ=S, extracted from the MULT=2S+1
given in $CONTRL.
* * * The following determine the state symmetry * * *
GROUP = name of the point group. The default is to copy
this from $DATA, if that group is Abelian (C1, Ci,
Cs, C2, C2v, C2h, D2, or D2h). If not, the point
group used will be C1 (no symmetry).
STSYM = specifies the spatial symmetry of the state.
Of course these names are the standard group
theory symbols for irreducible representations:
C1 A
Ci Ag Au
Cs AP APP (P stands for prime, i.e. ')
C2 A B
C2v A1 A2 B1 B2
C2h Ag Bu Bg Au
D2 A B1 B2 B3
D2h Ag B1g B2g B3g Au B1u B2u B3u
Default is STSYM being the totally symmetric
state, listed as the first column above.
The free format scanner is not able to read quotes
so the letters "P" must be used in Cs.
IRREPS = specifies the symmetries of the GLIST=SACAS space
determinant list. This variable should always be
an array, as a single symmetry is more quickly
obtained by the regular full CI code. The values
given are more primitive than STSYM, being the
following integers, not strings:
IRREPS= 1 2 3 4 5 6 7 8 meaning
C1 A
Ci Ag Au
Cs A' A''
C2 A B
C2v A1 A2 B1 B2
C2h Ag Bu Bg Au
D2 A B1 B2 B3
D2h Ag B1g B2g B3g Au B1u B2u B3u
* * * the following control the diagonalization * * *
NSTATE = Number of CI states to be found, including the
ground state. The default is 1, meaning ground
state only. The maximum number of states is 100.
See also IROOT below (two places).
PRTTOL = Printout tolerance for CI coefficients, the
default is to print any larger than 0.05.
ANALYS = a flag to request analysis of the CI energy in
terms of single and double excitation pair
correlation energies. This is normally used in
CI computations, rather than MCSCF, and when the
wavefunction is dominated by a single reference,
as the analysis is done in terms of excitations
from the determinant with largest CI coefficient.
The defalt is .FALSE.
ITERMX = Maximum number of Davidson iterations per root.
The default is 100. A CI calculation will fail
if convergence is not obtained before reaching
the limit. MCSCF computations will not bomb
if the iteration limit is reached, instead the
last CI vector is used to proceed into the next
orbital update. In cases with very large active
spaces, it may be faster to input ITERMX=2 or 3
to allow the program to avoid fully converging
the CI eigenvalue problem during the early MCSCF
iterations. For small active spaces, it is
best to allow the CI step to be fully converged
on every iteration.
CVGTOL = Convergence criterion for Davidson eigenvector
routine. This value is proportional to the
accuracy of the coefficients of the eigenvectors
found. The energy accuracy is proportional to
its square. The default is 1.0E-5, but 1E-6 if
gradients, MPLEVL, CITYP, or FMO selected).
NHGSS = dimension of the Hamiltonian submatrix which
is diagonalized to obtain the initial guess
eigenvectors. The determinants forming the
submatrix are chosen on the basis of a low
diagonal energy, or if needed to complete a
spin eigenfunction. The default is 300.
NSTGSS = Number of eigenvectors from the initial guess
Hamiltonian to be included in the Davidson's
iterative scheme. It is seldom necessary to
include extra states to obtain convergence to
the desired states. The default equals NSTATE.
MXXPAN = Maximum number of expansion basis vectors in the
iterative subspace during the Davidson iterations
before the expansion basis is truncated. The
default is the larger of 10 or 2*NSTGSS. Larger
values might help convergence, do not decrease
this parameter below 2*NSTGSS.
CLOBBR = a flag to erase the disk file containing CI
vectors from the previous MCSCF iteration. The
default is to use these as starting values for
the current iteration's CI. If you experience
loss of spin symmetry in the CI step, reverse
the default, to always take the CI from the top.
Default = .FALSE.
* * * the following control the 1st order density * * *
The following pertain to CI calculations by CITYP=xxx (not
to the CI step within MCSCF jobs). Similar keywords apply
to MCSCF runs, see just below.
PURES = flag to say that IROOT and NGFLGDM just below
should count only those states whose S value is
a match to that implied by MULT in $CONTRL.
Thus, PURES=.TRUE. (the default) allows selection
of S1 as IROOT=2 (the second singlet), even if
there is a T1 state (and maybe others!) between
S0 and S1. Of course, NSTATE must be large
enough to reach S1 (at least 3, if there is a T1
between S0 and S1).
Setting PURES to .FALSE. ignores the spin of each
state when using IROOT and NFLGDM.
IROOT = the root whose density is saved on the disk file
for subsequent property analysis. Only one root
can be saved, and the default value of 1 means
the ground state. Be sure to set NFLGDM to form
the density of the state you are interested in!
IROOT has a similar meaning for MCSCF, see below.
NFLGDM = Array controlling each state's density formation.
0 -> do not form density for this state.
1 -> form density and natural orbitals for this
state, print and punch occ.nums. and NOs.
2 -> same as 1, plus print density over MOs.
3 -> same as 2, plus print properties for this
state (see $ELMOM, $ELPOT, et cetera).
The default is NFLGDM(1)=1,0,0,...,0 meaning
only ground state NOs are generated.
SAFLG = is a logical flag that determines whether or not
state averaged CI density matrices and natural
orbitals should be evaluated. Setting SAFLG=.TRUE.
will result in the evaluation of the state averaged
density matrix and NOs. The default .FALSE. means
generate state-specific densities according to the
NFLGDM input. See also WSTATE.
WSTATE = An array of up to 100 weights to be given to the
densities of each state in forming the average
density matrix. The default is to optimize a
pure ground state, WSTATE(1)=1.0,0.0,...,0.0.
Note that values given for WSTATE (during a CI
calculation) will only be used if SAFLG=.TRUE.
It should also be noted that any electronic state
that has a nonzero value for WSTATE but a zero
for NFLGDM will reset its value for NFLGDM to 1.
FSTATE = An array of up to 100 weights to be given to the
densities of each state in forming the average
density matrix used for QM-EFP polarization.
FSTATE is ignored unless PMTD1=.FALSE. in $CONTRL.
See also PURES. The default is to set FSTATE from
WSTATE if only the latter is given.
* * * the following control the state averaged * * *
* * * 1st and 2nd order density matrix computation * * *
The following keywords apply to the CI step within the
MCSCF iterations. See just above for similar inputs
pertaining to CITYP=xxx calculations.
PURES = a flag controlling the spin purity of the state
averaging. If true, the WSTATE array pertains
to the lowest states of the same S value as is
chosen by the MULT keyword in $CONTRL. In this
case, the value of NSTATE will need to be bigger
than the total number of weights given as WSTATE
if there are other spin states present at low
energies. If .FALSE., it is possible to state
average over more than one S value, which might
be of interest in spin-orbit coupling jobs.
State-averaged MCSCF gradient runs must use .TRUE.
The default is .TRUE.
WSTATE = An array of up to 100 weights to be given to the
densities of each state in forming the average.
The default is to optimize a pure ground state,
WSTATE(1)=1.0,0.0,...,0.0
A small amount of the ground state can help the
convergence of excited states greatly.
Gradient runs are possible only with pure states.
Be sure to set NSTATE above appropriately!
See also IDWREF just below.
IDWREF = The target state K used to control dynamically
adjusted MCSCF state weights. This keyword may
only be used for CISTEP=ALDET or CISTEP=ORMAS.
The default is 0, to use static WSTATE values.
Dynamic weights are updated every MCSCF iteration
by the formula:
WSTATE(n) = sech^2[-DWPARM*(E(n)-E(K))].
for n= state K and any other weighted states,
followed by a normalization to sum to unity.
The formula gives the largest weight to state K,
with decreasing weight given to states farther
away in energy. See Deskevich, Nesbitt, and
Werner, J.Chem.Phys. 120, 7281(2004).
If IDWREF is given, the values given in WSTATE
are used only to specify which roots should have
non-zero weights.
The target state is often the ground state, K=1,
but any other state may be used: often K=IROOT!
Converged dynamic weights will be passed to the
determinant MCQDPT program (becoming its default
WPTST) and to the state-averaged gradient/NACME
program.
DWPARM = the value of the energy parameter used by IDWREF.
The default is 2.0 eV.
IROOT = the MCSCF state whose energy will be used as the
desired value. (default=0)
The default means to use the average (according to
WSTATE) of all states as the FINAL energy, which
is not a physically meaningful quantity.
When given as non-zero, IROOT chooses a specific
state, ignoring any states with undesired spins,
see PURES above, and also ignoring any states of
the correct spin which were given no weight.
Any run doing either analytic state-specific
gradients in state-averaged runs, or a gradient by
numerical differentiation must pick the desired
specific IROOT value!
IROOT has a similar meaning for CI, see above.
FSTATE = An array of up to 100 weights to be given to the
densities of each state in forming the average
density matrix used for QM-EFP polarization.
FSTATE is ignored unless PMTD1=.FALSE. in $CONTRL.
See also PURES. The default is to set FSTATE from
WSTATE if only the latter is given.
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generated on 7/7/2017