# Overlay 2

IOp(2/9)

Printing of distance and angle matrices.

0 | Default: print if ≤50 atoms. |

1 | Do not print the distance matrix. |

2 | Print distance matrix. |

00 | Default: do not print. |

10 | Do not print the angle matrix. |

20 | Print the angle matrix, using z-matrix connectivity if possible. |

30 | Use cutoffs instead of the z-matrix for determining which angles to print. |

000 | Default: same as 100. |

100 | Do not print dihedral angles. |

200 | Print dihedral angles, using the z-matrix for connectivity info. |

300 | Print dihedral angles, using a distance cutoff for connectivity info. |

0000 | Default: print only for small cases. |

1000 | Do not print the Cartesian coordinates in the input orientation. |

2000 | Do print the Cartesian coordinates in the input orientation. |

IOp(2/10)

Tetrahedral angle fixing

0 | Default (don’t test). |

1 | Angles within 0.001 degree of 109.471 will be set to ACOS(-1/3). |

2 | Do not test for such angles. |

IOp(2/11)

Printing of z-matrix and resultant coordinates.

0 | Default (print if 50 atoms or less). |

1 | Print. |

2 | Don’t print. |

IOp(2/12)

Crowding abort control.

0 | Default (same as 1). |

1 | Abort the run for zero atomic distances only. |

2 | Abort the run if any atoms are within 0.5 Å. |

3 | Do not abort the run regardless of 0 distances. |

IOp(2/13)

Punch coordinates.

0 | No. |

1 | Yes, in ‘atoms’ format (3E20.12). Note: atoms will not take the atomic numbers, so they are not punched. |

2 | Yes, in format suitable for coord. input to Gaussian. The atomic numbers and coordinates are punched in (I2,3E20.12). |

IOp(2/14)

Internal coordinate linear independence.

0 | Default (same as 2). |

1 | Perform the test, but do not abort the job. |

2 | Do not perform the test. |

3 | If internal cords. are in use, test the variables for linear indep, and abort the job if they’re dep. |

10 | Compute nuclear forces as well as second derivatives for the test. This is not correct for the linear independence check, but is useful for debugging the derivative transformation routines. |

100 | Abort the job if the number of z-matrix variables is not exactly the number of degrees of freedom (i.e., this is not a full optimization). |

IOp(2/15)

Symmetry control.

-1 | Turns on symmetry; same as 0 for molecules but turns on assignment of space group operations for PBC. |

0 | Leave symmetry in whatever state it is presently in. |

1 | Unconditionally turn symmetry off. Note that symmetry is still called, and will determine the framework group. However, the molecule is not oriented. |

2 | Bring the molecule to a symmetry orientation, but then disable further use of symmetry. |

3 | Don’t even call Symm. |

4 | Call Symm once with loose cutoffs, symmetrize the resulting coordinates then confirm symmetry with tight cutoffs. |

5 | Recover the previous symmetry operations from the RWF, and confirm that the new structure has the same symmetry. |

6 | Same as 5, but get symmetry info from the checkpoint. |

00 | Default (10). |

10 | Do re-orientation for PBC. |

20 | Suppress re-orientation for PBC. |

100 | Turn on symmetry operations for PBC. |

IOp(2/16)

Action taken if the point group changes during an optimization.

0 | Default (3). |

1 | Keep going. |

2 | Keep going, and leave symmetry on, using the old symmetry. |

3 | Keep going, and leave symmetry on, using the new symmetry. |

4 | Abort the job. |

IOp(2/17)

Tolerance for distance comparisons in symmetry determination.

0 | Default (determined in the symmetry package, currently 1.d-8). |

N>0 | 10^{-N}. |

N<0 | 10^{N}, use same tolerance for orientation. |

IOp(2/18)

Tolerance for non-distance comparisons in symmetry determination.

0 | Default (determined in the symmetry package, currently 1.d-7). |

N>0 | 10^{-N}. |

N<0 | 10^{N}, use same tolerance for orientation. |

IOp(2/19)

Largest allowed point group, as Hollerith string.

IOp(2/20)

Number (1-3 for X-Z) of axis to help specify which subgroup of the type specified in IOp(2/19) to use.

IOp(2/21)

Atomic values to use in symmetry assignment/orientation.

0 | Default (221). |

1 | Atomic numbers. |

2 | Atomic masses. |

10 | Print symmetry coordinates to high precision. |

20 | Do not print symmetry coordinates to high precision. |

100 | Save standard orientation as input orientation. |

200 | Do not save standard orientation as input orientation. |

IOp(2/29)

Update of coordinates from current z-matrix.

0 | Default (1). |

1 | No. |

2 | Yes, but remove z-matrix. |

3 | Yes. |

IOp(2/30)

Read in vector of atom types (for debugging).

0 | No |

1 | Yes, format (50I2) |

IOp(2/40)

Save (initial) structure and possible constraints in RWF 698.

0 | Default (No). |

1 | Yes. |

2 | Pick up structure from RWF 698 on the checkpoint file. |

3 | Read in structure from input stream. |

IOp(2/41)

Force constants for harmonic constraints.

-2 | Read in force constants for each Cartesian coordinate. |

-1 | No constraints. |

0 | Default (no constraint unless reading constraint from checkpoint file). |

N | N/10^{6} Hartree/Bohr^{2}. |

IOp(2/42)

Count nearest neighbor interactions.

0 | No. |

N | Count atoms within N/100 Å as neighbors. |

IOp(2/43)

Print standard orientation to high precision.

0 | No. |

1 | Yes. |

IOp(2/44)

Control for symmetry package.

00 | Default (12, unless COM was specified, in which case 21). |

1 | Initially. |

2 | Do not rotate to principal axes. |

10 | Rotate to old axes for C1, Cs, and Ci. |

20 | Use principal axes for C1, Cs, and Ci. |

Last updated on: 21 October 2016. [G16 Rev. B.01]