$CPMCHF group (relevant for analytic RUNTYP=HESSIAN,NACME,CONICAL) This group controls the solution of the response equations, also called coupled perturbed multiconfiguration Hartree-Fock, for MCSCF wavefunctions. These are needed for analytic hessians (CISTEP=ALDET or ORMAS), or for state-averaged gradients or non-adiabatic coupling matrix element calculations. The full response equations are solved for hessians, while Z-vector equations are used for NACME and SA-gradients. The default converger is a (linear) conjugate gradient (CG) method, but three others may be chosen. Difficult cases might work upwards from the default CG method by: $cpmchf $end $cpmchf ipdir=50 $end $cpmchf gcro=.t. micit=5 kicit=10 $end $cpmchf gcrodr=.t. micit=10 kicit=5 $end $cpmchf gcrodr=.t. micit=30 kicit=10 reclin=.false. $end $cpmchf gcrodr=.t. micit=20 kicit=10 reclin=.false. prcchg=.true. prctol=1.0 $end $cpmchf gcro=.t. micit=50 kicit=100 prcchg=.true. prctol=1.0 $end where the last one is "the sledgehammer". The options shown in the next to last case very often work, and will be considerably faster than the last set, which should always work. GCRO will typically take many fewer iterations than CG, a measure of its robustness, but will use more machine time due to its microiterations. --- the next set apply to any CP-MCHF converger --- MAXIT = maximum iterations. (default=300) CPTOL = accuracy tolerance for cpmchf equations Ax=b. (compared to r/||b||, within orbital, CI, and state averaged components) (default=1.0D-07) PRCCHG = a flag to adjust the linear equation's preconditioning. (Default=.FALSE.) For ORMAS runs in particular, the standard preconditioner might lead to ill-conditioning with very small elements. If selected, any preconditioner elements below PRCTOL will be reset to a value of 1.0 PRCTOL = a tolerance to keep preconditioner elements, if PRCCHG is chosen. Default=1.0D-6 --- for RUNTYP=NACME --- NAPICK = a flag to select running through z-vector setup and choose which linear equations to solve. .TRUE. leads to z-vector linear equations. .FALSE. leads to non-z-vector linear equations. The z-vector equations are advantageous when the degrees of freedom exceeds the no. of electronic states involved in the state-averaging. (The defaults are set to enforce this option.) The z-vector equations are also advantageous when only a few NA couplings out of the total total possible couplings are of interest. If CISTEP=ORMAS, NAPICK=.TRUE. is forced. Selecting NAPICK=.TRUE. requires the choice of NA couplings in the NACST array (see below). (default=varies... see ROUTINE NACMEX for notes) NACST = an array that indicates which NA couplings to Calculate, if NAPICK is chosen. For example, if WSTATE in $DET contains at least four states, the NACME can be limited to state pairs 1<->2 and 3<->4 by NACST(1)=3,4, 1,2. Note that you should pick increasing order within any pair of states! The program always generates the state-specific gradient of every state with a non-zero WSTATE. (default=none) --- the next three choose the other CPMCHF convergers --- If none is selected, conjugate gradient (CG) is used. GCRODR = a flag to select Generalized Conjugate Residual with inner Orthogonalization with Deflated Restarting. (default=.FALSE.) GCRO = a flag to select Generalized Conjugate Residual with inner Orthogonalization. (default=.FALSE.) CGGCRO = a flag to alternate between GCRO and CG solvers. (default=.FALSE.) --- next apply only to GCRODR: RECLIN = a flag to select recycling of Krylov subspaces from the first linear equation. (recycle linear). The first CP-MCHF linear equation is solved and a recyclable subspace is generated. Then, after a projection of approximate solution across the subspace from the first system, the rest of the linear equations are solved. The recycled subspace may or may not give rapid convergence with fewer iterations. See MICIT and KICIT. (default=.TRUE.) --- next apply only to GCRODR,GCRO,CGGCRO: MICIT = total size of the Krylov expansion space, namely the number of micro-iterations within an overall iteration. While the MICIT variable has no limit, fifty or more micro-iterations start to become computationally unmanagable for larger systems. The default often must be increased for large systems or for geometries far from equilibrium. In addition, the GCRODR converger has a slightly modified scheme for the micro-iterations. In the first iteration, MICIT micro-iterations are performed in a GMRES(MICIT) iteration. However, for subsequent iterations, (MICIT-KICIT) micro-iterations are performed. (default=5, often increased to 20 or 30) KICIT = the size of the recyclable Krylov basis saved and modified from iteration to iteration, created from eigenvectors with small eigenvalues. If this space is too small, the run will experience ill-conditioning, but if too large, the search space includes ineffective parts. In case PRCCHG is chosen, make sure the number of vectors reset from small values does not exceed KICIT, if it does, increase KICIT. (default=5, usually small, e.g. 5-10 for GCRODR) (MICIT> KICIT for GCRODR) (KICIT>=MICIT for GCRO and CGGCRO) --- next apply only to (linear) CG: NACFAC = number of iterations before softening the current convergence tolerance by 1/3, for CG only. Use NACFAC=0 (or MAXIT) to prevent raising the from the initial CPTOL. (default=50) IPDIR = number of iterations before resetting the residual from a pseudo-residual to the true residual. This reset also resets the search directions, since keeping the old 'ill-rounded' directions is not very beneficial. If a run almost convergences but struggles in later iterations, IPDIR=50 is recommended. This option appears more useful for NACME rather than Hessian runs. (default=MAXIT) --- next apply only to CGGCRO: ITERA = the number of (linear) CG iterations to apply before alternation to the GCRO converger. (default=5) ITERB = the number of GCRO iterations to apply before alternation to the (linear) CG converger. (default=5) ========================================================== ==========================================================

generated on 7/7/2017