RMC Phonon Dynamics

A browser-based phonon calculator for RMCProfile ensembles — no install, no setup, no server. Open the page, pick your run folder, and get phonon band structures, animated 3D modes, and simulated neutron spectra in seconds.

What makes it different: the phonons come straight from your RMC ensemble — atomic configurations fitted to experimental total-scattering and diffraction data (real-space PDF + reciprocal-space S(Q)/Bragg). They are extracted from the displacement covariance of those configurations, so the dynamics are a direct consequence of the measured structure — not taken from a spectroscopy measurement (INS/Raman/IR) or a lattice-dynamics/DFT model.

▶️ Open the app — drthyang.github.io/rmc-phonon-dynamics

1. Visit the link above.
2. Click Select directory and choose your RMC ensemble folder (a numbered .rmc6f ensemble, or Frac*.txt configs with a companion .rmc6f).
3. Build a k-path on the Brillouin zone, set the temperature, and Run — the band structure, 3D modes, INS S(|Q|,E), and phonon DOS render right in your browser.

🔒 Your data never leaves your device. Run files are read and every calculation happens locally in your browser — nothing is ever uploaded to any server. It's a private, secure way to analyze unpublished data. (Your browser's folder picker may say “Upload”, but nothing is sent anywhere.)

⚡ Computed on your GPU. The phonon displacement-covariance S(k) → diagonalization runs on WebGPU, directly on your machine — fast, with no backend to install or wait on.

🖥️ Use a Chromium browser (Chrome or Edge): the app needs WebGPU and the File System Access API, which Firefox/Safari don't yet provide.

What it does

• Cell & symmetry — the space group is auto-detected with a tolerance ladder (P1 → … → F-43m) and Wyckoff labels; fold to the conventional or primitive cell or build a custom supercell, and optionally impose symmetry to pool symmetry-equivalent sites and enforce the required branch degeneracies.
• Interactive Brillouin zone — the true Wigner–Seitz zone for the chosen cell; click high-symmetry points to lay out a k-path.
• Phonon band structure — dispersion E(k) from the RMC displacement covariance, with a hover readout, drag-to-zoom, and soft-mode (imaginary-frequency) highlighting.
• 3D mode viewer — click a band point to animate that mode; ball-and-stick / spacefill / wireframe, bonds, displacement vectors, and per-element colours.
• Simulated INS + DOS — powder-averaged S(|Q|,E) heatmap with a kinematic cutoff, plus the phonon density of states.
• Fit quality — per-configuration Rw overview across X-ray and neutron S(Q) & G(r) plus Bragg, each as measured-vs-model overlays; flag and exclude poorly-fit configurations from the run.
• Export — phonopy-compatible band.yaml / band.json and S(Q,E) CSV.

Everything above runs 100% client-side — the hosted link is static files; there is no server doing the work.

Requirements

Just a Chromium-based browser (Chrome or Edge) — the app needs both WebGPU and the File System Access API (showDirectoryPicker). A secure context (the hosted HTTPS site, or http://localhost) is required. There is nothing to install to use the hosted app.

Run locally (optional)

Only needed for development — to use the app, just open the hosted link.

cd web
npm install
npm run dev          # open the printed http://localhost:5173
npm run validate     # science + UI-mapping tests
npm run build        # static build → web/dist/

See web/README.md for the in-app workflow and web/FEATURE_PARITY_REPORT.md for how the in-browser results map to the original Python implementation.

Repository layout

Path	Purpose
web/	The application — React + Vite + WebGPU (the hosted link above).
archive/	Retired Python engines (src/, src_gpu/), the FastAPI GUI (rmcph_gui/), the standalone viewer (viz/), design handoffs, and historical notes.
.github/workflows/	CI that builds web/ and deploys it to GitHub Pages on every push to main.

data/ and results/ are local-only (git-ignored).

References and acknowledgments

The data-processing pipeline (RMCProfile → phonopy YAML), INS simulation, DOS calculations, and the WebGPU 3D mode viewer were developed for this project by Tsung-Han Yang. The viewer follows the phonon-mode display convention of the phononwebsite project [4], which also underpins the original viewer kept in archive/viz/.

1. Dove, M. T. (1993). Introduction to Lattice Dynamics. Cambridge University Press.
2. Goodwin, A. L., Tucker, M. G., Dove, M. T., & Keen, D. A. (2004). Phonons from powder diffraction: A quantitative model-independent evaluation. Physical Review Letters, 93, 075502. https://doi.org/10.1103/PhysRevLett.93.075502
3. Tucker, M. G., Keen, D. A., Dove, M. T., Goodwin, A. L., & Hui, Q. (2007). RMCProfile: Reverse Monte Carlo for polycrystalline materials. Journal of Physics: Condensed Matter, 19, 335218.
4. Miranda, H. P. C. phononwebsite. https://github.com/henriquemiranda/phononwebsite

License

Released under the MIT License © 2026 Tsung-Han Yang.

This project is personal work, developed and maintained in my personal capacity.