Table of Contents
Since the new queue structure on scientific servers have time limits, the Gaussian calculations may be terminated prematurely due to inadequate length of time. To restart such a prematurely terminated calculation, one can use the check pointing facilitated via the Gaussian supported checkpointing file. However, note here that the primary use of a checkpoint file is to use the results of one calculation as the starting point for a second calculation.
When a Gaussian calculation is restarted using information from a checkpoint file, the new calculation results (or the continuation from the uncompleted run) will be placed in the exact same checkpoint file, overwriting the original checkpoint file. THUS IT IS ALWAYS SAFER TO MAKE A BACKUP COPY OF THE CHECKPOINT FILE. Note that it is possible for a checkpoint file to become corrupted (i.e. if a calculation dies while writing to the checkpoint file).
Gaussian will use a checkpoint file if the command:
%Chk=file_name
appears before the route card in the input file. If the specified file does not exist, it will be created. If the specified file does exist, information to be used in the present calculation can be read from it.
A calculation can be started using information from the checkpoint file by including one of the following commands in the route card.
ChkBasis |
Read the basis set from the checkpoint file. |
SCF=Restart |
Restart an SCF calculation from the checkpoint file. This is normally used when an SCF calculation failed finish for some reason. |
IRC=Restart |
Restarts an IRC calculation that did not complete, or restarts an IRC calculation for which additional points along the reaction path are desired. |
Scan=Restart |
Restarts a potential energy surface scan which did not complete. |
Freq=Restart |
Restarts a numerical frequency calculation which did not complete. Analytic frequency calculations cannot be restarted. |
Polar=Restart |
Restarts a numerical polarizability calculation which did not complete. |
CIS=Restart |
Restarts a CIS (Configuration Interaction - Single excitation) calculation which did not complete. |
Opt=Restart |
Restarts an geometry optimization which did not complete. |
Geom=Checkpoint |
Reads the molecular geometry from the checkpoint file. |
Geom=AllCheckpoint |
Reads the molecular geometry, charge, multiplicity and title from the checkpoint file. This is often used to start a second calculation at a different level of theory. |
Guess=Read |
Reads the initial guess from the checkpoint file. If the basis set specified is different from the basis set used in the job which generated the checkpoint file, then the wave function will be projected from one basis to the other. This is an efficient way to switch from one basis to another. |
Density=Checkpoint |
Reads the density from the checkpoint file. This inplies Guess=Only so that no integrals or SCF are computed. This is used to compute the population analysis or create cube files from a wave function without rerunning the job. |
Field=Checkpoint |
Reads the 34 multipole components of a finite field from the checkpoint file. |
Field=EChk |
Reads the 3 electric dipole field components from the checkpoint file. |
Charge=Check |
Reads point charges from the checkpoint file. |
ReArchive |
This option is used to generate an archive entry from the information in the checkpoint file. No calculation is run. |
Copyright 2002-2007 The University of North Carolina at Chapel Hill.
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