Technical Support Information
Last update: 26 September 2006

Overlay 2

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IOp(2/9)

Printing of distance and angle matrices.

0        Default: same as 2.

1        Do not print the distance matrix.

2        Print distance matrix.

00       Default: same as 20.

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 A.

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 FORMAT (I2,3E20.12)

IOp(2/14)

Internal coordinate linear independance.

0        Default (same as 2).

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

2        Do not perform the test.

3        If internal coordinates are in use, test the variables for linear independance and abort the job if they are dependant.

10       Compute nuclear forces as well as second derivatives for the test. This is not correct for the linear
           independance 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 ops. for PBC.

0        Leave symmetry in whatever state it is presently in.

1        Unconditionally turn symmetry off. Note that symm 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 chk.

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(19) to use.

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 rwf698 on the chk file.

3        Read in structure from input stream.

IOp(2/41)

Force constants for Harmonic constraints.

-2        Read in force constants for each cartesian coordinates

-1        No constraints.

0          Default (no constraint unless reading constraint from chk file).

N         N/1000 Hartree/Bohr**2