9.2.5 Libopt3Job Control‣ 9.2 Geometry Optimization Job Controls ‣ Chapter 9 Exploring Potential Energy Surfaces: Searches for Critical Points and Molecular Dynamics ‣ Q-Chem 6.1 User’s Manual

Within Libopt3 there is a separate $geom_opt section for geometry optimization job controls, which provide greater control then the GEOM_OPT variables. This new section contains all the following input variables for the LIBOPT3 driver.

ALGORITHM
       Specifies which type of minimization algorithm to use.
INPUT SECTION: $geom_opt
TYPE:
       STRING
DEFAULT:
       BFGS (OPT) / BOFILL (TS)
OPTIONS:
       SD Steepest Descent CG Conjugate Gradient Newton Exact Newton’s Method BFGS Broyden-Fletcher-Goldfarb-Shanno ¹⁴⁶ Broyden C. G.
SIAM J. App. Math.
(1970), 6, pp. 76. Link ^, ¹¹¹⁴ Shanno D. F.
Math. Comp.
(1970), 24, pp. 647. Link ^, ⁴¹⁵ Goldfarb G.
Math. Comp.
(1970), 24, pp. 23. Link ^, ³⁴⁶ Fletcher R.
Comput. J.
(1970), 13, pp. 317. Link LBFGS Limited-memory BFGS SR1 Symmetric-Rank One (Murtagh-Sargent) ⁸⁶⁹ Murtagh B. A., Sargent R. W. H.
Comput. J.
(1970), 13, pp. 185. Link PSB Powell symmetric Broyden BOFILL Bofill combination of PSB and SR1 ¹²⁷ Bofill J. M.
J. Comput. Chem.
(1994), 15, pp. 1. Link FS Farkas and Schlegel combination of SR1 and BFGS ³³⁷ Farkas Ö., Schlegel H. B.
J. Chem. Phys.
(1999), 111, pp. 10806. Link
RECOMMENDATION:
       Steepest descent and conjugate gradient methods are slow to converge in general but are useful when the near the minimum. Best to start with other algorithms and finalize with these two methods if a tighter converged minimum is needed. Newton’s will be efficient but requires a Hessian evaluation at each step, so the cost of the Hessian calculation must be accounted for when using exact Newton’s method. BFGS is a default algorithm for jobtype = OPT for its speed and efficiency for finding the minimum. L-BFGS is recommended when dealing with very large systems when memory is of concern. The default algorithm for jobtype = TS is Bofill.

COORDINATES
       Specifies which type of coordinate system to use for optimization.
INPUT SECTION: $geom_opt
TYPE:
       STRING
DEFAULT:
       Delocalized
OPTIONS:
       Cartesian Cartesian Coordiantes Redundant Redundant Internal Coordinates Delocalized Delocalized Natural Internal Coordinates
RECOMMENDATION:
       Cartesian can be more stable than internal coordinates but are generally slower than internal coordinates. If there are problems with internal coordinate optimization restart with Cartesian coordinates at the last known internal coordinate geometry can be controlled with OPTIMIZATION_RESTART.

MAXITER
       Maximum number of geometry optimization cycles.
INPUT SECTION: $geom_opt
TYPE:
       INTEGER
DEFAULT:
       50
OPTIONS:
       Integer Any positive integer
RECOMMENDATION:
       None

INITIAL_HESSIAN
       Specifies the type of initial Hessian to use.
INPUT SECTION: $geom_opt
TYPE:
       STRING
DEFAULT:
       SIMPLE (OPT) / EXACT (TS)
OPTIONS:
       Identity Identity Matrix Simple Simple Approximate Guess Hessian Model Model Approximate Guess Hessian Exact Analytical Hessian Read Read-in Hessian
RECOMMENDATION:
       The initial guess Hessian for Cartesian coordinates is a unit matrix where for internal coordinates it is an approximate Hessian based on the internal coordinates. ⁶⁰ Bakken V., Helgaker T.
J. Chem. Phys.
(2002), 117, pp. 9160. Link The model approximate Hessian is based on a force constant matrix. ¹⁰⁹² Schlegel H. B.
Theor. Chem. Acc.
(1984), 66, pp. 333. Link ^, ¹³²⁹ Wittbrodt J. M., Schlegel H. B.
J. Mol. Struct. (Theochem)
(1997), 398, pp. 55. Link The exact Hessian is always a quality initial Hessian but could be costly but can be calculated at the start of the optimization or read in from scratch. The default for OPT is the simple approximate guess Hessian but for TS the Exact analytical Hessian will be used.

CONVERGENCE_CHECK
       Specifies the type of convergence check during geometry optimization.
INPUT SECTION: $geom_opt
TYPE:
       STRING
DEFAULT:
       DEFAULT
OPTIONS:
       Default Check max absolute gradient component and ( maximum absolute displacement or change in energy) Energy Change in energy Gradient Check norm of gradient
RECOMMENDATION:
       None.

GRADIENT_CONVERGENCE
       The value of maximum absolute gradient or norm of gradient for convergence check.
INPUT SECTION: $geom_opt
TYPE:
       FLOAT
DEFAULT:
       3e-4
OPTIONS:
       Float Any positive float
RECOMMENDATION:
       This variable is used as the comparison value for the gradient checked with CONVERGENCE_CHECK.

DISPLACEMENT_CONVERGENCE
       The value of maximum absolute displacement for convergence check.
INPUT SECTION: $geom_opt
TYPE:
       FLOAT
DEFAULT:
       1.2e-3
OPTIONS:
       Float Any positive float
RECOMMENDATION:
       None.

ENERGY_CONVERGENCE
       The value of maximum absolute energy difference for convergence check.
INPUT SECTION: $geom_opt
TYPE:
       FLOAT
DEFAULT:
       1e-6
OPTIONS:
       Float Any positive float
RECOMMENDATION:
       None.

STEP_LIMITER
       Specifies the type of limiter to use for adjustment of the step during geometry optimization.
INPUT SECTION: $geom_opt
TYPE:
       STRING
DEFAULT:
       RMS (OPT) / NORM (TS)
OPTIONS:
       RMS Root mean square of the step NORM Norm of the step
RECOMMENDATION:
       Adjust the type of condition used for MAX_DISPLACEMENT.

MAX_DISPLACEMENT
       The value of maximum for the STEP_LIMITER of the Eigenvector following algorithm step.
INPUT SECTION: $geom_opt
TYPE:
       FLOAT
DEFAULT:
       3e-1
OPTIONS:
       Float Any positive float
RECOMMENDATION:
       If this value is too large there may be trouble with the optimization and a small value could require additional optimization cycles.

RECOMPUTE_HESSIAN
       Recompute the exact Hessian during optimization algorithms
INPUT SECTION: $geom_opt
TYPE:
       STRING
DEFAULT:
       False
OPTIONS:
       None Do not recompute of Hessian Recompute Compute Hessian during optimization
RECOMMENDATION:
       Recompute the exact Hessian during optimization during BFGS, SR1, PSB, BOFILL, and FS Quasi-Newton Hessian update algorithms.

RECOMPUTE_HESSIAN_CYCLES
       The number of cycles before recomputing the Hessian during optimization algorithms.
INPUT SECTION: $geom_opt
TYPE:
       INTEGER
DEFAULT:
       5
OPTIONS:
       Integer Any positive integer
RECOMMENDATION:
       None.

STEP_SEARCH_ALGORITHM
       Specifies the type of algorithm for geometry step generation.
INPUT SECTION: $geom_opt
TYPE:
       STRING
DEFAULT:
       EFA
OPTIONS:
       EFA Eigenvector Following Algorithm LS Simple Line Search
RECOMMENDATION:
       For Quasi-Newton methods the default step generation is Eigenvector following algorithm, but line search can be used if desired.

EIGENVECTOR_ALGORITHM
       Specifies the type of Eigenvector algorithm.
INPUT SECTION: $geom_opt
TYPE:
       STRING
DEFAULT:
       RFO
OPTIONS:
       RFO Rational Function Optimization PRFO Partitioned Rational Function Optimization
RECOMMENDATION:
       This allows the switching of the Eigenvector following algorithm for state specific searches with PRFO.

PRINT_LEVEL
       Specifies the printing verbosity of the optimizer.
INPUT SECTION: $geom_opt
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 General Print 10 Verbose
RECOMMENDATION:
       None.

MAX_LBGFGS_HISTORY
       Specifies the number of cycles to retain for L-BFGS history.
INPUT SECTION: $geom_opt
TYPE:
       INTEGER
DEFAULT:
       10
OPTIONS:
       Integer Any positive integer
RECOMMENDATION:
       It is recommended to keep this number small.

LS_PARAM
       Specifies the type of line search algorithm to use.
INPUT SECTION: $geom_opt
TYPE:
       STRING
DEFAULT:
       Quasi-Newton
OPTIONS:
       Quasi-Newton Quasi-Newton Strict Strict line search parameters Very_Strict Very strict line search parameters
RECOMMENDATION:
       None

LS_MAXITER
       Specifies the number of maximum iterations to perform during line search step calculation.
INPUT SECTION: $geom_opt
TYPE:
       INTEGER
DEFAULT:
       10
OPTIONS:
       Integer Any positive integer
RECOMMENDATION:
       None

LS_PRINT
       Specifies the verbosity of printing for the line search algorithm.
INPUT SECTION: $geom_opt
TYPE:
       String
DEFAULT:
       Minimal
OPTIONS:
       Minimal Minimal printing Verbose Verbose printing
RECOMMENDATION:
       None

HESSIAN_VERIFY
       Specifies the type of verification with the Hessian after geometry optimization
INPUT SECTION: $geom_opt
TYPE:
       STRING
DEFAULT:
       RESULT
OPTIONS:
       No_Verification Do no verification of optimization Result Verify with final Hessian obtained during optimization Without Verify without a Hessian (Only convergence criteria) Recomputed Verify with recomputed exact Hessian
RECOMMENDATION:
       None.

OPTIMIZATION_RESTART
       Specifies if optimization should restart in Cartesian coordinates after back-transformation failure with internal coordinate optimizations.
INPUT SECTION: $geom_opt
TYPE:
       STRING
DEFAULT:
       TRUE
OPTIONS:
       True Restart with Cartesian Coordinates False Do not restart
RECOMMENDATION:
       Restart a failed back-transformation internal coordinate optimization job in Cartesian coordinates. This will use the current retained updated Internal coordinate Hessian transform it to Cartesian coordinates and continue the optimization from the last known position.

FINAL_ZMAT_PRINT
       Controls if a Z-matrix is printed at the end of the job.
INPUT SECTION: $geom_opt
TYPE:
       STRING
DEFAULT:
       TRUE
OPTIONS:
       True Construct Z-matrix and print False Do calculate or print Z-matrix
RECOMMENDATION:
       After optimization the final structure can be used to compute and print the final Z-matrix. This can be turned off if molecule contains many atoms and Z-Matrix is not needed.

FINAL_VIBRATIONAL_ANALYSIS
       Run Vibrational Analysis after geometry optimization.
INPUT SECTION: $geom_opt
TYPE:
       STRING
DEFAULT:
       False
OPTIONS:
       True Perform Vibrational Analysis False Do not compute vibrational analysis
RECOMMENDATION:
       Vibrational analysis can be performed only if the final Hessian for verification was recomputed, HESSIAN_VERIFY

PRINT_TOPOLOGY
       Print the topology for optimization.
INPUT SECTION: $geom_opt
TYPE:
       STRING
DEFAULT:
       FALSE
OPTIONS:
       True Print the topology False Do not print the topology Terminate Print the topology and terminate job
RECOMMENDATION:
       Print the topology used in optimization. In addition the topology can be printed then the job terminated.

USER_TOPOLOGY
       Specifies if a user provided topology is to be read.
INPUT SECTION: $geom_opt
TYPE:
       STRING
DEFAULT:
       Generated
OPTIONS:
       Generated Generate the topology Read Read a user provided topology.
RECOMMENDATION:
       A user can provide a topology for a given molecule in the $geom_opt_topology section in the input.

A user defined topology can be read in using the USER_TOPOLOGY keyword and providing the topology in $geom_opt_topology section. The available topology definitions that can be used are:

1 (Bond): A-B
2 (Angle): A-C-B (Apex is B)
4 (Torsion): Torsion A-B-C-D
5 (Co-Linear Angle) use with 6: D A-B-C (ABC is Linear)
6 (Co-Linear Angle) use with 5: D A-B-C (ABC is Linear)

Note: The first line is the total number of coordinates to read. Then the following lines are the coordinate definition to be used, following the definition above: coordinate type, atom number 1, ….

$geom_opt_topology
Total Number of Coordinates
1   atomA  atomB !Bonds
...
2   atomA  atomC  atomB !Angles
...
4   atomA  atomB  atomC atomD !Torsions
...
5   atomD  atomA  atomB atomC !Co-linear Torsion
...
6   atomD  atomA  atomB atomC !Co-linear Torsion
$end

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9.2.5 Libopt3 Job Control