Gaussian Esp Vmd

Gaussian ESP with Multiwfn and VMD

Use this skill for one or more .fch files when the requested deliverables include density/ESP cubes, ESP surface statistics, or ESP images.

Preconditions

• Input layout: fch/.fch; output root: output//.
• Locate Multiwfn in this order: valid MULTIWFN_BIN, Multiwfn on PATH, then a location explicitly supplied by the user. Do not assume a local install path.
• For images, locate VMD in the same way using VMD_BIN; Pillow is required to convert TGA to PNG.
• Preflight each dependency before the stage that needs it. Preserve existing final outputs unless the user explicitly requests overwrite.

Per-molecule workflow

Run the bundled entry point from the recipient's analysis folder (which contains fch/):

python /scripts/run_esp.py --input fch --output output --render

The skill carries its own Multiwfn and VMD templates; do not use this repository's root scripts/ folder.

1. Create an isolated temporary working directory and output//; copy or reference only fch/.fch there. Log Multiwfn to output//multiwfn_esp.log.
2. In Multiwfn, use the established ESP isosurface input to export both density.cub and totesp.cub. Return to the main menu and quit cleanly; do not rely on EOF to end the program.
3. Verify that both temporary cubes are newly created, then move them to:

• _density.cub
• _ESP.cub

1. Use Multiwfn's surface-analysis function to calculate ESP statistics and the electron-density-isosurface extents. Save _esp_stats.txt and _dimensions.txt. State the selected isovalue in the data file.
2. Only if graphics are requested and VMD/Pillow are available: render _ESP.cub headlessly to a temporary _ESP.tga, passing the measured ESP surface minimum and maximum from step 4 as VMD's color scale; convert it to _ESP.png, verify the PNG, and remove the temporary TGA. Never silently use a fixed ESP color range.

Required checks

• Stop if Multiwfn exits unsuccessfully or either cube is absent; never continue with old files or suppress the error. Multiwfn 3.8 Windows builds can report a post-analysis Fortran return code 59 after printing Surface analysis finished!; accept that code only when the ESP extrema and all three dimensions were parsed and the log contains that completion marker.
• Do not claim that this skill produces HOMO/LUMO energies; those belong to $gaussian-frontier-orbitals.
• Report a concise summary per molecule: 2 cube files, optional 1 PNG, 2 ESP/dimension TXT files, and the VMD render log when graphics are requested.

Failure handling

• Missing Multiwfn: ask for MULTIWFN_BIN or an installation location.
• Missing VMD/Pillow: keep valid cubes and TXT files, report that only the optional graphics stage was skipped.
• Missing or invalid ESP surface extrema: keep the cubes and statistics, skip the ESP image, and report that the color scale could not be determined.
• Long analyses: write logs to disk and report progress only per completed molecule rather than streaming verbose Multiwfn output.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: Nanhuai-X
• Source: Nanhuai-X/gaussian-molecule-workflow
• License: MIT

Install and usage instructions live in the source repository linked above.