@occ/core

JavaScript/WebAssembly bindings for OCC - a quantum chemistry and crystallography library.

Installation

npm install @occ/core

Quick Start

const { loadOCC, createMolecule, Elements } = require('@occ/core');

// Initialize the WASM module
const Module = await loadOCC();

// Create a water molecule
const water = await createMolecule(
  [Elements.O, Elements.H, Elements.H],
  [
    [0.0, 0.0, 0.0],
    [0.757, 0.586, 0.0],
    [-0.757, 0.586, 0.0]
  ]
);

console.log(`Molecule: ${water.name}`);
console.log(`Atoms: ${water.size()}`);
console.log(`Molar mass: ${water.molarMass()} g/mol`);

Features

• Molecular Structure Manipulation: Create and manipulate molecular structures
• Quantum Chemistry Calculations: Hartree-Fock, DFT, and post-HF methods
• Crystallography: Space groups, symmetry operations, and crystal structure analysis
• Partial Charges: EEM and EEQ charge models
• Geometry Analysis: Point groups, molecular properties, and transformations
• Isosurface Generation: Electron density and promolecule density visualization
• Custom Logging: Flexible logging system with callbacks and buffering

Command-line interface (WASM)

The full occ CLI ships as a WebAssembly ES module (dist/occ.wasm + dist/occ.js).

Under node it runs directly against your working directory (inputs are read from, and outputs written to, the current directory):

npx occ scf water.xyz "ccsd(t)" 6-31g

Programmatic use (node, browser, or a { type: 'module' } worker):

import createOccCliModule from '@peterspackman/occjs/cli';

const M = await createOccCliModule({ noInitialRun: true, locateFile: ... });
M.FS.writeFile('/water.xyz', xyzContents);
const exitCode = M.callMain(['scf', 'water.xyz', 'ccsd(t)', '6-31g']);

Migrating from ≤0.9.x: occ.js used to be a classic script configured through a global Module object and loaded with importScripts(). It is now a modularized ES module with a default-exported createOccCliModule factory — pass your configuration as its argument and spawn workers with { type: 'module' }. See examples/occ-run-worker.js for the pattern.

Development

Building from Source

1. Prerequisites: Ensure you have Emscripten installed
2. Build WASM module: npm run build:wasm
3. Build JavaScript wrapper: npm run build:wrapper
4. Run tests: npm test

Testing

# Run all tests
npm test

# Run tests in watch mode
npm run test:watch

# Run tests with coverage
npm run test:coverage

# Run linting
npm run lint

# Run type checking
npm run typecheck

Available Test Suites

• Core functionality: Basic module loading and error handling
• Logging: Log level management and message handling
• Molecular structure: Molecule creation and property access
• Quantum chemistry: Hartree-Fock, DFT calculations, and property analysis
• Crystallography: Space groups, symmetry operations, unit cells
• Isosurfaces: Surface generation and cube file export
• Basis sets: Built-in and custom JSON basis set loading

Documentation

For complete API documentation, examples, and usage guides, see the main OCC repository.

Links

• GitHub Repository
• Documentation
• Issue Tracker