DRC print options

The amount of output in the DRC is controlled by three sets of options. These sets are:

Equivalent Keywords H-PRIORITY, T-PRIORITY, and X-PRIORITY.
Potential Energy Turning Point option.
Geometry Maxima Turning Point options.

If T-PRIORITY is used then turning points cannot be monitored.

To monitor geometry turning points, put a "T" in place of the geometry optimization flag for the relevant geometric variable. In the example shown in the Figure, the geometry of formaldehyde would first be optimized, then a FORCE calculation run, then a DRC calculation started, using the first normal mode for the starting velocity. Whenever the C=O bond length becomes a maximum or a minimum, a message is printed.

Figure:
Example of DRC calculation, monitoring a geometric variable

 IRC=1 DRC T=20
 Formaldehyde
 Monitoring the C=O Bond-length turning points
  O    0.0 0    0.0 0    0.000000 0   0 0 0
  C    1.2 T    0.0 0    0.000000 0   1 0 0
  H    1.0 1  120.0 1    0.000000 0   2 1 0
  H    1.0 1  120.0 1  180.000000 0   2 1 3
  0    0.0 0    0.0 0    0.000000 0   0 0 0

To monitor the potential energy turning points, put a "T" for the flag for atom 1 bond length (Do not forget to put in a bond-length (zero will do)!).

To monitor the geometry, use LARGE=n. This will cause the geometry to be printed once every n steps.

The effect of using these flags together is as follows.

1. No options: All calculated points will be printed. No turning points will be calculated.
2. Atom 1 bond length flagged with a "T": If T-PRIO, etc. are NOT specified, then potential energy turning points will be printed.
3. Internal coordinate flags set to "T": If T-PRIO, etc. are NOT specified, then geometry extrema will be printed. If only one coordinate is flagged, then the turning point will be displayed in chronologic order; if several are flagged then all turning points occurring in a given time-interval will be printed as they are detected. In other words, some may be out of chronologic order. Note that each coordinate flagged will give rise to a different geometry: minimize flagged coordinates to minimize output.
4. Potential and geometric flags set: The effect is equivalent to the sum of the first two options.
5. T-PRIO set: No turning points will be printed, but constant time-slices (by default 0.1 fs) will be used to control the print.