*OPTIMIZATION

Purpose:

To change defaults for optimization of an MCSCF wave function. Some of the options also affect a QC-HF optimization.

.ABSORPTION

READ (LUINP,'(A8)') RWORD
RWORD = ` LEVEL 1', ` LEVEL 2', or ` LEVEL 3'
Orbital absorption in MCSCF optimization at level 1, 2, or 3, as specified (normally level 3, see comments below). This keyword may be repeated to specify more than one absorption level, the program will then begin with the lowest level requested and, when that level is converged, disable the lower level and shift to the next level.

.ACTROT

include specified active-active rotations

  READ (LUINP,*) NWOPT
  DO I = 1,NWOPT
    READ (LUINP,*) JWOP(1,I),JWOP(2,I)
  END DO

JWOP(1:2,I) denotes normal molecular orbital numbers (not the active orbital numbers).

.ALWAYS ABSORPTION

Absorption in all MCSCF macro iterations (default is to disable absorption in local region or after ".MAXABS" macro iterations, whichever comes first). Absorption is always disabled after Newton-Raphson algorithm has been used, and thus also when doing ".CORERELAX", because absorption may cause variational collapse if the desired state is excited.

.CI PHP MATRIX

Default : MAXPHP = 1 (Davidson's algorithm)
READ (LUINP,*) MAXPHP
PHP is a subblock of the CI matrix which is calculated explicitly in order to obtain improved CI trial vectors compared to the straight Davidson algorithm. The configurations corresponding to the lowest diagonal elements are selected, unless ".PHPRESIDUAL" is specified. MAXPHP is the maximum dimension of PHP, the actual dimension will be less if MAXPHP will split degenerate configurations.

.COREHOLE

READ (LUINP,*) JCHSYM,JCHORB
JCHSYM = symmetry of core orbital
JCHORB = the orbital in symmetry JCHSYM with a single core hole
Single core hole MCSCF calculation. The calculation must be of RAS type with only the single core-hole orbital in RAS1, the state specified with ".STATE" is optimized with the core-hole orbital frozen. The specified core hole orbital must be either inactive or the one RAS1 orbital, if it is inactive then it will switch places with the RAS1 orbital and it will not be possible to also specify ".REORDER". If explicit reordering is required you must reorder the core orbital yourself and let JCHORB point to the one RAS1 orbital. Orbital absorption is activated at level 2. See comments below for more information.

.CORERELAX

(ignored if ".COREHOLE" isn't also specified)
Optimize state with relaxed core orbital (using Newton-Raphson algorithm, it is not necessary to explicitly specify ".NR ALWAYS"). It is assumed that this calculation follows an optimization with frozen core orbital and that the orbital has already been moved to the RAS1 space (i.e., the specific value of "JCHORB" under ".COREHOLE" is ignored). Any orbital absorption will be ignored.

.DETERMINANTS

Use determinant basis instead of CSF basis (see comments).

.EXACTDIAGONAL

Default for RAS calculations.
Use the exact orbital Hessian diagonal.

.FOCKDIAGONAL

Default for CAS calculations.
Use an approximate orbital Hessian diagonal which only uses Fock contributions.

.FOCKONLY

Activate TRACI option (default : program decides).
Modified TRACI option where all orbitals, also active orbitals, are transformed to Fock type orbitals in each iteration.

.FROZEN CORE ORBITALS

READ (LUINP,*) (NFRO(I),I=1,NSYM)
Frozen orbitals : Number of inactive (doubly occupied) orbitals to be frozen in each symmetry (the first NFRO(I) in symmetry I) in MCSCF. Active orbitals and specific inactive orbitals can be frozen with ".FREEZE" under *ORBITAL INPUT. Frozen orbitals in SCF are specified in the *SCF INPUT input module.

.MAX CI

READ (LUINP,*) MAXCIT
maximum number of CI iterations before MCSCF (default = 3).

.MAX MACRO ITERATIONS

READ (LUINP,*) MAXMAC
maximum number of macro iterations in MCSCF optimization (default = 15).

.MAX MICRO ITERATIONS

READ (LUINP,*) MAXJT
maximum number of micro iterations per macro iteration in MCSCF optimization (default = 24).

.MAXABS

READ (LUINP,*) MAXABS
maximum number of macro iterations with absorption (default = 3).

.MAXAPM

READ (LUINP,*) MAXAPM
maximum number orbital absorptions within a macro iteration (APM : Absorptions Per Macro iteration; default = 5)

.NATONLY

Activate TRACI option (default : program decides).
Modified TRACI option where the inactive and secondary orbitals are not touched (these two types of orbitals are already natural orbitals).

.NEO ALWAYS

Always norm-extended optimization (never switch to Newton-Raphson). Note: ".NR ALWAYS" and ".CORERELAX" takes precedence over ".NEO ALWAYS".

.NO ABSORPTION

Never orbital absorption (default settings removed)

.NO ACTIVE-ACTIVE ROTATIONS

No active-active rotations in RAS optimization.

.NOTRACI

Disable TRACI option (default : program decides).

.NR ALWAYS

Always Newton-Raphson optimization (never NEO optimization). Note: ".NR ALWAYS" takes precedence over ".NEO ALWAYS".

.OLSEN

Use Jeppe Olsen's generalization of the Davidson algorithm.

.OPTIMAL ORBITAL TRIAL VECTORS

Generate "optimal" orbital trial vectors [21].

.ORB_TRIAL VECTORS

Use also orbital trial vectors as start vectors for auxiliary roots in each macro iteration (CI trial vectors are always generated).

.PHPRESIDUAL

Select configurations for PHP matrix based on largest residual rather than lowest diagonal elements.

.SIMULTANEOUS ROOTS

Default : NROOTS = ISTATE, LROOTS = NROOTS
READ (LUINP,*) NROOTS, LROOTS
NROOTS = Number of simultaneous roots in NEO
LROOTS = Number of simultaneous roots in NEO at start

.STATE

Default = 1
READ (LUINP,*) ISTATE
Index of MCSCF Hessian at convergence (1 for lowest state, 2 for first excited state, etc. within the spatial symmetry and spin symmetry specified under *CONFIGURATION INPUT).

.SYM CHECK

Default: ICHECK = 2 when NROOTS $>$ 1, else ICHECK = -1.
READ (LUINP,*) ICHECK
Check symmetry of the LROOTS start CI-vectors and remove those which have wrong symmetry (e.g. vectors of delta symmetry in a sigma symmetry calculation).

  ICHECK < 0  : No symmetry check.
  ICHECK = 1  : Remove those vectors which do not have the same
                symmetry as the ISTATE vector, reassign ISTATE.
  ICHECK = 2  : Remove those vectors which do not have the same
                symmetry as the lowest state vector before selecting
                the ISTATE vector.
  other values: check symmetry, do not remove any CI vectors.

The ".SIMULTANEOUS ROOTS" input will automatically be updated if CI vectors are removed.

.THRCGR

READ (LUINP,*) THRCGR
Threshold for print of CI gradient. Default is 0.1D0.

.THRESH

Default = 1.0D-05
READ (LUINP,*) THRMC
Convergence threshold for energy gradient in MCSCF optimization. The convergence of the energy will be approximately the square of this number.

.TRACI

Activate TRACI option (default : program decides).
Active orbitals are transformed to natural orbitals and the CI-vectors are counter-rotated such that the CI states do not change. The inactive and secondary orbitals are transformed to Fock type orbitals (corresponding to canonical orbitals for closed shell Hartree-Fock). For RAS wave functions the active orbitals are only transformed within their own class (RAS1, RAS2, or RAS3) as the wave function is not invariant to orbital rotations between the classes. For RAS, the orbitals are thus not true natural orbitals, the density matrix is only block diagonalized. Use ".IPRCNO" (see p. ) to control output from this transformation.

Comments:

COREHOLE: Single core-hole calculations are performed as RAS calculations where the opened core orbital is in the RAS1 space. The RAS1 space must therefore contain one and only one orbital when the COREHOLE option is used, and the occupation must be restricted to be exactly one electron. The orbital identified as the core orbital must be either inactive or the one RAS1 orbital, if it is inactive it will switch places with the one RAS1 orbital. The core orbital (now in RAS1) will be frozen in the following optimization. After this calculation has converged, the CORERELAX option may be added and the core orbital will be relaxed. When CORERELAX is specified it is assumed that the calculation was preceded by a frozen core calculation, and that the orbital has already been moved to the RAS1 space. Default corresponds to the main peak, shake-up energies may be obtained by specifying ".STATE" larger than one. Absorption is very beneficial in core hole calculations because of the large orbital relaxation following the opening of the core hole.

ABSORPTION: Absorption level 1 includes occupied - occupied rotations only (including active-active rotations); level 2 adds inactive - secondary rotations and only active - secondary rotations are excluded at this level; and finally level 3 includes all non-redundant rotation for the frozen CI vector. Levels 1 and 2 require the same integral transformation (because the inactive - secondary rotations are performed using the P-supermatrix integrals) and level 1 is therefore usually not used. Level 3 is the normal and full level, but it can be advantageous to activate level 2 together with level 3 if big inactive-active or occupied-occupied rotations are expected.

ORB_TRIAL: Orbital trialas start vectors can be used for excited states and other calculations with more than one simultaneous roots. The orbital start trial vectors are based on the eigenvectors of the NEO matrix in the previous macro iterations. However, they are probably not cost-effective for multiconfiguration calculations where optimal orbital trial vectors are used and they are therefore not used by default.

SYM CHECK: The symmetry check is performed on the matrix element $\langle VEC1 \mid oper \mid VEC2\rangle$, where "oper" is the CI-diagonal. It is recommended and the default to use ".SYM CHECK" for excited states, including CI vectors of undesired symmetries is a waste of CPU time.

DETERMINANTS: The kernels of the CI sigma routines and density matrix routines are always performed in determinant basis. However, this keyword specifies that the external representation is Slater determinants as well. The default is that the external representation is in CSF basis as described in chapter 8 of MOTECC-90. The external CSF basis is generally to be preferred to be sure that the converged state(s) have pure and correct spin symmetry, and to save disk space. It is recommended to specify ".PLUS COMBINATIONS" under "*CI VECTOR" for calculations on singlet states with determinants, in particular for excited singlet states which often have lower lying triplet states.