$GEN group (required by MCSCF if CISTEP=GENCI) $CIDET group (required if CITYP=ALDET, ORMAS, or FSOCI) $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. ========================================================== ==========================================================

generated on 7/7/2017