chkchk

The chkchk utility displays the route and title sections from a checkpoint file, and indicates other information that is present within it. It is useful for determining the contents of random checkpoint files whose purpose has been forgotten and whose names are non-descriptive. It takes the name of the checkpoint file as its argument. Here is an example of its use:

$ chkchk important
 Checkpoint file important.chk:
 Title:  Opt freq for pentaprismane
 Route:  #P opt freq b3lyp/6-311+g(2d,p) 
 Version:  ES64L-G16RevB.01
 NAtoms=      4 ICharg=     0 Multip=     1
 Atomic coordinates present.
 AO basis is present.
 MO coefficients present.
 Cartesian force constants present.
 This checkpoint is from a job which completed successfully.
 Internal force constants may be present.
 An OT bucket is present. The stored data is from a(n) Optimization job.
   Total number of points stored =         1.
   Number of statistics per point=         2.

The -p option may be used to print additional information from the checkpoint file, including the molecular coordinates, the basis set in Gen format, and the molecular orbitals in the correct format for Guess=Cards. This information may be redirected to a file for later use as input to Gaussian or another program.

Here is an example:

 $ chkchk -p myfile >newjob.gjf   
 $ cat newjob.gjf   
  Checkpoint file myfile.chk:   
  Title:  DMABN: Opt freq from saddle point found by first opt: acetonitrile   
  Route:  #N Geom=AllCheck Guess=TCheck SCRF=Check GenChk    
          B3LYP/6-311+G(2d,p) Freq   
  Atomic coordinates (Angstroms):  Molecular structure 
     0    1   
   N   2.258424299166     -0.051967437933     -0.108610457679   
   C   0.911965883667     -0.011528021623     -0.025315883831   
   …   
    
  AO basis set (Overlap normalization):   Basis set in format for Gen keyword 
  Atom N1       Shell     1 S   6     bf    1 -     1   4.267803417278   -0.098204225521   -0.205244020181 
  Atom N1  Shell  1 S   6   bf    1 -   1   4.26780   -0.09820   -0.20524  
       0.6293480000D+04  0.1969788147D-02   
       0.9490440000D+03  0.1496128592D-01   
       …   
  Atom N1       Shell     2 SP   3    bf    2 -     5   4.267803417278   -0.098204225521   -0.205244020181 
  Atom N1  Shell   2 SP   3   bf    2 -   5   4.26780   -0.09820   -0.20524     
       0.3063310000D+02  0.1119060795D+00  0.3831191864D-01   
       …   
     
 (5D15.8)   MOs in format for Guess=Cards 
     1 Alpha MO OE=-0.15587059D+02   
  0.55760173D+00 0.46815568D+00-0.15193125D-03 0.20920429D-03 0.73161643D-03   
  0.58391570D-02-0.61620240D-04-0.80819280D-04-0.30786697D-03-0.40418785D-02   
  …   
    
   357 Alpha MO OE= 0.37351112D+02   
  0.81138955D-01-0.87165085D-01 0.52591067D-03 0.25976528D-03-0.27428643D-03   
  0.35549516D-01-0.44238173D-02-0.13061602D-02 0.11962956D-02-0.14464014D+00   
    
  Input for Opt=FCCards (Energy,Forces,Force Constants):   Forces for use with Opt=FCCards
  -0.4554698501440964D+03   
   0.00000485  0.00000348  0.00000040 -0.00000441  0.00000421 -0.00000731   
   0.00000048  0.00000292 -0.00000191 -0.00000112  0.00000014 -0.00000354   
   …   
    
  Internal force constants may be present.   
  An OT bucket is present. The stored data is from a(n) Optimization job.   
    Total number of points stored =         1.   
    Number of statistics per point=         2.   

Note that some editing of the generated input file may be required prior to use.