optking(1)

📦 version 3.4.0, in debian bookworm, ubuntu jammy, ubuntu noble

👑 optking(1) 👑

okay so bestie, this is the manual for optking(1) — the program that does geometry optimization and force constant evaluation. it's giving computational chemistry realness. let's get into it. 💅

✨ DESCRIPTION ✨

The program optking may be used to optimize geometries in internal coordinates, to make internal coordinate displacements, or to determine vibrational frequencies at stationary points. The following sets of coordinates may be used:

  1. a set of internal coordinates may be provided by the user in intco.dat. The format is described in the INTCO manpage and is the same as that used by bmat and intder95. Only the STRE, BEND, TORS, and OUT keywords are currently supported by optking.
  2. a redundant set of simple internal coordinates may be generated by optking based on bond-connectivity. This is the default set of coordinates for optimizations. The simple coordinates are taken from the z-matrix if zmat_simples=true.
  3. a set of symmetry-adapted (limited to D2h), nonredundant, delocalized internal coordinates can be automatically generated by optking. These coordinates may become somewhat nonorthogonal as the geometry changes during an optimization. Used if delocalize=true.
  4. a set of coordinates similar to those above may be generated from a set of simple internal coordinates provided by the user. These simples may be directly put in intco.dat or inferred from the z-matrix (if zmat_simples=true and delocalize=true).
  5. symmetry-adapted cartesian coordinates are used to compute frequencies by finite differences.

💅 COMMAND LINE ARGUMENTS 💅

After internal coordinates are detected or generated, optking will enter a run-time mode dependent on command line arguments.

  • --opt_step — take an ordinary geometry optimization step
  • --disp_nosymm — displaces along all internals, assumes no sym
  • --disp_irrep — displaces along all internals labeled as IRREP
  • --disp_load — load a previous displacement from PSIF to chkpt
  • --load_ref — load undisplaced reference geometry into chkpt
  • --freq_energy — compute frequencies from energies (not yet supported)
  • --grad_energy — use energies to compute a gradient
  • --freq_grad_nosymm — use grads in chkpt to compute freqs, assumes no sym
  • --freq_grad_irrep — use grads in chkpt to compute IRREP freqs
  • --grad_save — save the gradient in chkpt to PSIF list
  • --energy_save — save the energy in chkpt to PSIF list
  • --disp_num — displacement index (by default read from PSIF)
  • --points — 3 or 5 pt formula (5 pt not yet supported)
  • --irrep — the irrep (1,2,...) being displaced or computed

Force constants are read from fconst.dat, if possible, or else are empirically generated. Currently, the program has no special transition state searching methods such as any other Hessian update besides the BFGS update.

Changes of Note 💀

  1. All information which optking uses is read from the chkpt file (32) or optking's own psifile (1). The only exception is that initial force constants (if provided) are read from fconst.dat.
  2. The file intco.dat is an optional starting file. As a result, it will be written to by optking as necessary. The file intco.dat should have a last line containing only ")" if you need optking to supply coordinates.
  3. Coordinates to be fixed may be placed in a fixed_intco: section of the input file or alternatively inferred from the z-matrix. See the Users Manual for more information.

🌸 REFERENCES 🌸

  1. Geometry optimization in redundant internal coordinates, P. Pulay and G. Fogarasi, J. Chem. Phys. 96, 2856 (1992).
  2. Using redundant internal coordinates to optimize equilibrium geometries and transition states, C. Peng, P. Y. Ayala, H. B. Schlegel, and M. J. Frisch, J. Comp. Chem. 17, 49 (1996).
  3. The generation and use of delocalized internal coordinates in geometry optimization, J. Baker, A. Kessi and B. Delley, J. Chem. Phys. 105, 192 (1996).
  4. Estimating the Hessian for gradient-type geometry optimizations, H. B. Schlegel, Theoret. Chim. Acta (Berl.) 66, 333 (1984).

🎀 FILES REQUIRED 🎀

  • input.dat — input file

🦋 OPTIONAL INPUT FILES 🦋

  • intco.dat — either just simple internals
    • or also linear combinations
  • fconst.dat — Hessian or force constant matrix
  • opt.aux — Hessian update information

💜 TEMPORARY FILES USED 💜

  • none

🔥 FILES UPDATED 🔥

  • intco.dat — if internals are not provided by user
  • fintco.dat — internal coordinates to be frozen - generated from zmat
  • fconst.dat — stores current updated Hessian matrix
  • output.dat — output file

⭐ INPUT FORMAT ⭐

Input for this program is read from the OPTKING section of the file input.dat. The following keywords are valid:

DISPLACEMENTS = vector of vectors

If DISPLACMENTS keyword is present, then a geometry optimization is not being performed, but internal coordinate displacements are being made. There is no default. Each element of this vector is a vector consisting of internal coordinate indices and displacement values. The units of displacement are angstrom and radians. For example, if you desire two displacements, the first being a displacement of internal coordinate 1 by 0.01 angstroms, the second a combination of coordinate 1 displaced by 0.01 angstroms and coordinate 2 by 0.05 angstroms, the DISPLACEMENTS vector would be:

                 displacements = (
                   (1 0.01)
                   (1 0.01 2 0.05)
                 )

CONV = integer

The test for convergence of the geometry optimization is that the maximum force on an internal coordinate (in aJ/Ang or aJ/Rad) must be less than 10^(-CONV). The default is 5.

EV_TOL = integer

When primitive internals are being delocalized there must be 3n-6 (linear 3n-5) nonzero eigenvalues of the G matrix corresponding to nonredundant delocalized coordinates. Eigenvalues greater than 10^(-EV_TOL) are considered nonzero. The default is 5.

REDUNDANT = boolean

If true, then redundant coordinates are permitted. The default for geometry optimizations is true. However, if delocalize is set to true, or finite differences are being computed, redundant is set to false.

DELOCALIZE = boolean

If true, then delocalized internals are generated. The default is false, unless first derivatives are being determined by energy points. If the SYMM vector is given by the user, this keyword has no effect.

SYMMETRY = string

In order to delocalize coordinates, character table information is required. For compatibility to old-input, the keyword SYMMETRY is searched for in the DEFAULT section. If absent, it is read from PSIF_CHKPT (presumably successfully if input3.0 or later was used).

BFGS = boolean

If true, then a BFGS Hessian update is performed when possible. The default is true.

MIX_TYPES = boolean

If true, then generated delocalized coordinates will mix all primitive internal types. The default is true.

JUNK_30 = boolean

If true, then the last iterated geometry from the back-transformation to cartesian coordinates will be written to PSIF_CHKPT, even if the back-transformation did not converge.

BONDS = vector of atom pairs

This array contains bonds which need to be added to the primitive internal coordinate set.

NOBONDS = vector of atom pairs

This array contains bonds which need to be deleted from the primitive internal coordinate set.

The following print options provide additional output. They may help the user understand the workings of the program (The default for each is false.)

If simple internals are automatically generated, prints the related info.

prints values for all of the optking input parameters.

If automatic delocalized coordinates are formed, prints the related info.

prints an abundance of symmetry related information.

The following keywords are parameters for the back-transformation from internal coordinates to cartesian coordinates. These should rarely be needed.

BT_MAX_ITER = integer

Maximum number of iterations. Default is 100.

BT_DQ_CONV = integer

Subsequent changes in internal coordinates must be less than 10^(-BT_DQ_CONV). The default is 11.

BT_DX_CONV = integer

Subsequent changes in cartesian coordinates must be less than 10^(-BT_DX_CONV). The default is 11.

And that's the whole vibe bestie! This manual page is from 30 Jul, 2002 and it's for optking(1) — periodt. 💖✨

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