ECCE

The Extensible Computational Chemistry Environment (ECCE, pronounced "etch-ā"; ecce is Latin for "behold") is a graphical environment for computational chemistry: build a molecule, set up a calculation, run it on your own computer or a cluster, and look at the results (orbitals, densities, vibrations, geometry optimisations), with every calculation kept in one place.

It works with ORCA, Gaussian, NWChem, MOPAC and xTB, and experimentally with GROMACS, CP2K and Quantum ESPRESSO; ECCE 9 also includes ECCE-QM, a small built-in Hartree–Fock/DFT program that needs nothing else installed. Calculations can be chained into workflows: for example, xTB finds a structure quickly and ORCA refines it, each step starting from the geometry of the one before. ECCE was developed at Pacific Northwest National Laboratory, which stopped supporting it around 2017; it is maintained here since, with PNNL's blessing.

More pictures and the full feature list: ECCE overview.

Get ECCE

Download from the releases page.

• ECCE 9 (latest 9.5.1), for Linux, macOS and Windows: the recommended version. The macOS and Windows clients are experimental.
• ECCE 8.18.x (latest 8.18.14), Linux only: the older line, which still gets bug fixes.

System	File	Install
Debian 13, Ubuntu 24.04	ecce-client_…deb, ecce-server_…deb	sudo apt install ./ecce-client_*.deb ./ecce-server_*.deb
RHEL/Rocky 9, Fedora	ecce-client-…rpm, ecce-server-…rpm	sudo dnf install ./ecce-*.rpm (on RHEL/Rocky first sudo dnf install epel-release)
macOS	ECCE-…-arm64.dmg (Apple silicon) or …-x86_64.dmg (Intel, macOS 10.15 or later) or …-x86_64-macos10.13.dmg (Intel, macOS 10.13 and 10.14; experimental)	open it and drag ECCE to Applications; macOS refuses it at first: on macOS 15 and later open it once, then System Settings → Privacy & Security → Open Anyway (macOS 14 and earlier: right-click → Open), or run xattr -dr com.apple.quarantine /Applications/ECCE.app
Windows 10/11	ECCE-windows-….msi	double-click; at the SmartScreen warning choose More info → Run anyway

Then start ecce (on macOS and Windows: ECCE in Applications or the Start menu). Details for each system: Installing ECCE.

Coming in 9.5.2

On main, not in a package yet:

• DirDyVTST, Polyrate and Amica are no longer supported (#873); existing calculations still open.
• Example set Workflows: the Na+(H2O)6 workflow gets a water (CPCM) ORCA step after each gas-phase ORCA step, starting from that step's geometry and Hessian; a workflow step can start from the source's ORCA Hessian (Start from the source's Hessian).
• Workflows: an Auto-run checkbox runs the remaining steps once the first one is launched, and a play button on each box runs that step (#736); the Protonation Sites recipe no longer warns that CREST needs an optimised structure, and the step after CREST gets the protomer (#851).
• General Chemistry examples: Packing in solids, with simple cubic Po, bcc Na, fcc Al and Cu, and hcp Mg shown as unit cells (#859); Quantum ESPRESSO pw.x outputs can be imported (#447).
• Dipole Moment: an optional Bond dipoles display splits the dipole into bond contributions from a chosen set of atomic charges, as purple arrows on the bonds and a table with the point-charge sum, the computed dipole and the remainder (#849).
• NWChem MD: a task after an optimisation starts from the optimised structure (.qrs), not from the restart the optimisation was given; dynamics with SHAKE no longer aborts (#865).
• ORCA: RI approximation None, RIJCOSX or RIJONX (#834); orbital views (Density Map, Density Profile, density fields) work for basis sets with g functions (#861).
• Reaction rates: ecce-rate gives conventional transition-state-theory rate constants with Wigner and Eckart tunnelling, reverse rate, equilibrium constant, and Arrhenius and Eyring fits over a temperature range, from reactant, transition-state and product calculations of any code (#872). Workflows with reactant, TS and product steps show the rate in a Rate box (with a temperature range window and CSV export), and the Reaction overview takes a -> [ts] -> c and charts the barrier and lists k.
• Fragment orbitals: ecce-fragorb analyse expands each MO of a complex in the orbitals of fragment calculations at the same geometry (Mulliken or SCPA shares, connections above a threshold), and ecce-fragorb dos gives PDOS, TDOS and overlap-population DOS (OPDOS) for atom sets (#201, #171).
• Command line: ecce-ensemble pick takes the N lowest distinct members of a CREST ensemble and checks each against the input (protonation, counter-ions, metal contacts), ecce-ensemble minimum finds the lowest-G minimum among conformer calculations, and ecce-ensemble benchmark makes a log K table against experiment (#836).
• Energy Calculator: a 1 M standard-state term on G and a log K line (#835). ecce-rerun --last-geometry continues a running calculation from its last geometry with new cores and wall time (#837).
• CREST quantum cluster growth runs show their progress (#862); multiplicity 9 is "Nonet" (#853); the side panel keeps its width between panels (#843); Density Map controls tidied (#852).
• Every finished calculation with orbitals gets a results.h5 stored beside it, checked (tr(PS) and orthonormality) on every write; the Density Map, Density Profile and density-field command read the orbitals from it. ecce-results write makes one for an older calculation (#690).
• Builder: Tools > Add from SMILES... builds a molecule with its formal charges and stereochemistry from ECCE's own SMILES reader and builder (no Open Babel needed, #867), optionally in a fully extended start, and Replace Group... swaps a selected terminal group for a SMILES fragment, with the rotation about the bond chosen to avoid clashes (#833).
• Terminate: a program that outlives the queue's cancel is ended too, and the message says whether anything is still running in the run directory (#855).
• Structure Library organised by chemistry: small organic molecules, natural products and drugs, biomolecules, inorganic, teaching (#405).

The order of the remaining work is on the Work plan. What 9.5.0 brought: release notes.

First steps

The same pages are in ECCE under Help. To see it done first, the chem4eva YouTube channel has short videos with subtitles: installing ECCE, a first calculation with ECCE-QM (nothing else to install) and a first ORCA calculation.

1. Installation: what you see the first time ECCE starts, and where your work is kept.
2. Your first calculation: build, run and look at a calculation.
3. Running codes on Linux, on Windows or on macOS: installing NWChem, MOPAC, ORCA and the others, and telling ECCE where they are.
4. Importing a structure or a calculation that ran elsewhere.
5. Scripting and AI assistants: the command-line tools and the AGENTS.md file that says how to work with ECCE's data.

Getting help and reporting a problem

Questions, and how you use ECCE, are welcome in Discussions. Run the session that goes wrong with ecce --bug. When it ends, ECCE collects its logs into ~/ecce-bug-<time>.zip (no passwords, but host names, user names and paths). Attach that to a new issue, with what you did and what you expected.

For administrators and developers

• Getting started: building, packaging, a central server for a group or class, TLS, the other deployment modes, upgrading from 8.x.
• Contributing: building from source, branches and releases, the roadmap, and how to help.
• Changes: what is new in 9.0 and in 8.x, and the release history.
• The wiki: where things are in the code, and the current work plan.
• Accessibility: what ECCE does for keyboard, screen reader and low-vision use, and how to report a barrier.

Citing ECCE

Please cite the DOI for all versions, 10.5281/zenodo.23281771; each release also has its own DOI there. GitHub's "Cite this repository" button gives the reference in APA and BibTeX form.

License

ECCE is free software under the Educational Community License 2.0; see LICENSE. For the use of the name, see TRADEMARKS.md.