9.2.2 Optimize Job Control

GEOM_OPT_HESSIAN
       Determines the initial Hessian status.
TYPE:
       STRING
DEFAULT:
       DIAGONAL
OPTIONS:
       DIAGONAL Set up diagonal Hessian. 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 is expensive to compute.

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.