`RESTART`

When a job has been stopped, for whatever reason, and intermediate results have been stored, then the calculation can be restarted at the point where it stopped by specifying RESTART. The most common cause of a job stopping before completion is its exceeding the time allocated. A saddle-point calculation has no restart, but the output file contains information which can easily be used to start the calculation from a point near to where it stopped.

The restart file contains all the geometry data: current geometry, cycle number, gradient and Hessian information, if calculated, etc. It does not contain information on the atoms, so the restart data set has to have a normal geometry just like a non-restart data set. This is used only for supplying the atom-types and number of atoms..

Example: If the following data set is run, it will stop after three geometry optimization cycles, and output a message indicating that restart files have been created.

cycles=3
Ethanol
C2H5OH
O
C 1.5 1 0 0 0 0 1
C 1.5 1 120 1 0 0 2 1
H 1.0 1 120 1 90 1 1 2 3
H 1.0 1 109 1 120 1 2 1 3
H 1.0 1 109 1 240 1 2 1 3
H 1.0 1 109 1 0 1 3 2 1
H 1.0 1 109 1 120 1 3 2 1
H 1.0 1 109 1 240 1 3 2 1

By adding the word "RESTART" to the original data set, and re-submitting the job, the calculation can be continued. In this example, "cycles=3" has been deleted; this allows the job to run to completion.

restart
Ethanol
C2H5OH
O
C 1.5 1 0 0 0 0 1
C 1.5 1 120 1 0 0 2 1
H 1.0 1 120 1 90 1 1 2 3
H 1.0 1 109 1 120 1 2 1 3
H 1.0 1 109 1 240 1 2 1 3
H 1.0 1 109 1 0 1 3 2 1
H 1.0 1 109 1 120 1 3 2 1
H 1.0 1 109 1 240 1 3 2 1

It is not necessary to change the geometric data to reflect the new geometry, although this can be done, if desired. When RESTART is used, the <file>.res file contains all the geometric data, and this will immediately over-write the geometry supplied by the data set. Note, however, that the data set must have a geometry because the <file>.res file does not contain the atom types. A convenient way to monitor a long run is to specify 1SCF and RESTART; this will give a normal output file at very little cost.

Note: Two restarts exist in the IRC calculation. If an IRC calculation stops while in the FORCE calculation, then a normal restart can be done. If the job stops while doing the IRC calculation itself then the keyword IRC=n should be changed to IRC, or it can be omitted if DRC is also specified. The absence of the string "IRC=" is used to indicate that the FORCE calculation was completed before the restart files were written.