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Your first analysis

Install openWFN, open a packaged example, and save your first result. This walkthrough uses water. The same steps apply to other supported files when they contain the data needed for the analysis.

Prerequisites

  • Python 3.10–3.13
  • A terminal

1. Install openWFN

python -m pip install --upgrade openwfn
openwfn --version

Use python -m pip so installation and execution refer to the same Python environment. Record the installed version when reproducing an analysis.

2. Copy the packaged examples

The package includes a water example and an eleven-molecule Molden collection. Copy them into the current directory; no repository download is needed:

openwfn examples install ./openwfn-examples

The command refuses to replace an existing fixture unless you pass --overwrite.

3. Read the molecular summary

openwfn ./openwfn-examples/water.fchk summary

Check the formula, atom count, charge and multiplicity in the summary. Energy and other fields appear when the file contains them. Use --format json to read the complete result in a script.

To try a different format, open the packaged ethanol example:

openwfn ./openwfn-examples/everyday-qc/ethanol.molden summary

For guided mode in an interactive terminal, use the same file with open instead of summary. Scripts should use direct commands or analyze.

The center of mass is reported in ångströms and energy in hartree. Bond count comes from openWFN's covalent-radius perception; it is not a bond-order assignment.

4. Measure the molecular geometry

CLI atom indices are one-based:

openwfn ./openwfn-examples/water.fchk geometry distance 1 2
openwfn ./openwfn-examples/water.fchk geometry angle 2 1 3

Confirm atom ordering from the source calculation or the guided interactive atom table before measuring an unfamiliar system.

5. Save a machine-readable result

openwfn --format json --output water-summary.json \
  ./openwfn-examples/water.fchk summary

JSON keeps the complete result: values, units, warnings, validation status and source information. Use it in scripts or keep it with your research notes.

6. Record reproducibility information

Keep the input checksum, openWFN version, command and settings with your results. You can also create a report to read or share:

openwfn ./openwfn-examples/water.fchk report build water-report.html

Troubleshooting

  • command not found: activate the environment where you installed openWFN or run python -m pip show openwfn to locate it.
  • missing record: the selected analysis needs a record absent from this input file.
  • .chk conversion failure: install Gaussian's formchk or provide an .fchk file.
  • browser does not open: open the generated HTML file manually; generation may still have succeeded.

Next steps