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: Optimization and frequencies for pentaprismane
 Route: #T BECKE3LYP/6-31+G(D,P) OPT FREQ POP=FULL
 Atomic coordinates present.
 SCF restart data present.
 This file appears to be from the middle of a restartable job.
 Internal force constants may be present.

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 a Gaussian input file.

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
      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
      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 will generally be required prior to use.