FCHK (.fchk)

Background & Context

    • MIME type: chemical/x-gaussian-checkpointGaussian-formatted checkpoint file.
    • Plain-text version of the binary checkpoint file.
    • Used to store result of quantum chemistry calculation results.
    • Plain text format.
    • Maintained by Gaussian, Inc.


  • Import["file.fchk"] imports an FCHK file as a Molecule object.
  • See the reference pages for full general information on Import.
  • ImportString supports the FCHK format.

Import Elements

  • General Import elements:
  • "Elements"list of elements and options available in this file
    "Rules"full list of rules for each element and option
  • Data elements:
  • "Molecule"a symbolic representation of the molecule model
    "Metadata"an Association containing results from the file
  • Results such as molecular-orbital energies and occupation are stored in the "Metadata".
  • The calculation results are also included in the "Molecule" element. Use mol["MetaInformation"] to retrieve them from the molecule mol.
  • Three-dimensional coordinates from the file are stored in the molecule in the AtomCoordinates option value.
  • Use mol["AtomCoordinates"] to retrieve the coordinates from the imported molecule mol.


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Basic Examples  (1)

Import an FCHK file as a molecule:

Show the molecule in 3D:

Dipole and orbital information is stored in the molecule's MetaInformation:

Scope  (2)

Import the molecule and get the computed dipole moment:

Show the dipole together with a 3D plot of the molecule:

Find the wavelength of light corresponding to a molecule's band gap using the formula:

Import the molecule and get the computed dipole moment:

Find the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO):

Find the energy required to promote an electron from HOMO to LUMO:

Use FormulaData to convert to wavelength:

Convert the result to nanometers:

Visualize the result as a color: