9.2.2 Optimize Job Control

GEOM_OPT_HESSIAN
       Determines the initial Hessian status.
TYPE:
       STRING/INTEGER
DEFAULT:
       $-$1
OPTIONS:
       $-$1 Approximate Hessian based on the force constant matrix (same as the “Model” option in Libopt3) READ Have exact or initial Hessian. Use as is if Cartesian, or transform if internals.
RECOMMENDATION:
       An accurate initial Hessian will improve the performance of the optimizer, but it may be expensive to compute. Note that more options for the initial Hessian are available in Libopt3, controlled by INITIAL_HESSIAN under the $geom_opt section (see Sec. 9.2.5).

GEOM_OPT_COORDS
       Controls the type of optimization coordinates.
TYPE:
       INTEGER
DEFAULT:
       $-$1
OPTIONS:
        0 Optimize in Cartesian coordinates.  1 Generate and optimize in internal coordinates, if this fails abort. $-$1 Generate and optimize in internal coordinates, if this fails at any stage of the optimization, switch to Cartesian and continue.  2 Optimize in $Z$-matrix coordinates, if this fails abort. $-$2 Optimize in $Z$-matrix coordinates, if this fails during any stage of the optimization switch to Cartesians and continue.
RECOMMENDATION:
       Use the default, as delocalized internals are more efficient. Note that optimization in $Z$-matrix coordinates requires that the input be specified in $Z$-matrix format.

GEOM_OPT_TOL_GRADIENT
       Convergence on maximum gradient component.
TYPE:
       INTEGER
DEFAULT:
       300 $\equiv 300\times {10}^{-6}$ tolerance on maximum gradient component.
OPTIONS:
       $n$ Integer value (tolerance = $n\times {10}^{-6}$).
RECOMMENDATION:
       Use the default. To converge GEOM_OPT_TOL_GRADIENT and one of GEOM_OPT_TOL_DISPLACEMENT and GEOM_OPT_TOL_ENERGY must be satisfied.

GEOM_OPT_TOL_DISPLACEMENT
       Convergence on maximum atomic displacement.
TYPE:
       INTEGER
DEFAULT:
       1200 $\equiv 1200\times {10}^{-6}$ tolerance on maximum atomic displacement.
OPTIONS:
       $n$ Integer value (tolerance = $n\times {10}^{-6}$).
RECOMMENDATION:
       Use the default. To converge GEOM_OPT_TOL_GRADIENT and one of GEOM_OPT_TOL_DISPLACEMENT and GEOM_OPT_TOL_ENERGY must be satisfied.

GEOM_OPT_TOL_ENERGY
       Convergence on energy change of successive optimization cycles.
TYPE:
       INTEGER
DEFAULT:
       100 $\equiv 100\times {10}^{-8}$ tolerance on maximum (absolute) energy change.
OPTIONS:
       $n$ Integer value (tolerance = value $n\times {10}^{-8}$).
RECOMMENDATION:
       Use the default. To converge GEOM_OPT_TOL_GRADIENT and one of GEOM_OPT_TOL_DISPLACEMENT and GEOM_OPT_TOL_ENERGY must be satisfied.

GEOM_OPT_MAX_CYCLES
       Maximum number of optimization cycles.
TYPE:
       INTEGER
DEFAULT:
       50
OPTIONS:
       $n$ User defined positive integer.
RECOMMENDATION:
       The default should be sufficient for most cases. Increase if the initial guess geometry is poor, or for systems with shallow potential wells.

GEOM_OPT_PRINT
       Controls the amount of Optimize print output.
TYPE:
       INTEGER
DEFAULT:
       3 Error messages, summary, warning, standard information and gradient print out.
OPTIONS:
       0 Error messages only. 1 Level 0 plus summary and warning print out. 2 Level 1 plus standard information. 3 Level 2 plus gradient print out. 4 Level 3 plus Hessian print out. 5 Level 4 plus iterative print out. 6 Level 5 plus internal generation print out. 7 Debug print out.
RECOMMENDATION:
       Use the default.

GEOM_OPT_SYMFLAG
       Controls the use of symmetry in Optimize.
TYPE:
       LOGICAL
DEFAULT:
       TRUE
OPTIONS:
       TRUE Make use of point group symmetry. FALSE Do not make use of point group symmetry.
RECOMMENDATION:
       Use the default.

GEOM_OPT_MODE
       Determines Hessian mode followed during a transition state search.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Mode following off. $n$ Maximize along mode $n$.
RECOMMENDATION:
       Use the default, for geometry optimizations.

GEOM_OPT_MAX_DIIS
       Controls maximum size of subspace for GDIIS.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Do not use GDIIS. -1 Default size = min(NDEG, NATOMS, 4) NDEG = number of molecular degrees of freedom. $n$ Size specified by user.
RECOMMENDATION:
       Use the default or do not set $n$ too large.

GEOM_OPT_DMAX
       Maximum allowed step size. Value supplied is multiplied by 10${}^{-3}$.
TYPE:
       INTEGER
DEFAULT:
       300 = 0.3
OPTIONS:
       $n$ User-defined cutoff.
RECOMMENDATION:
       Use the default.

GEOM_OPT_UPDATE
       Controls the Hessian update algorithm.
TYPE:
       INTEGER
DEFAULT:
       -1
OPTIONS:
       -1 Use the default update algorithm.  0 Do not update the Hessian (not recommended).  1 Murtagh-Sargent update.  2 Powell update.  3 Powell/Murtagh-Sargent update (TS default).  4 BFGS update (OPT default).  5 BFGS with safeguards to ensure retention of positive definiteness (GDIIS default).
RECOMMENDATION:
       Use the default.

GEOM_OPT_LINEAR_ANGLE
       Threshold for near linear bond angles (degrees).
TYPE:
       INTEGER
DEFAULT:
       165 degrees.
OPTIONS:
       $n$ User-defined level.
RECOMMENDATION:
       Use the default.

FDIFF_STEPSIZE
       Displacement used for calculating derivatives by finite difference.
TYPE:
       INTEGER
DEFAULT:
       100 Corresponding to 0.001 Å. For calculating second derivatives.
OPTIONS:
       $n$ Use a step size of $n\times {10}^{-5}$.
RECOMMENDATION:
       Use the default except in cases where the potential surface is very flat, in which case a larger value should be used. See FDIFF_STEPSIZE_QFF for third and fourth derivatives.