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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 10N, 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 10N, 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/106 Hartree/Bohr2.

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. C.01]