Range calculator in the browser

The range calculator runs the ion transport of this book in your browser, as WebAssembly on one thread. Give it an ion, an energy and an elemental target; it returns the projected range $R_p$, the straggle $\Delta R_p$ and a depth profile. It is a static page: there is no server, and nothing you enter leaves your machine.

A run of $10^4$ 5 keV B ions into Si takes a few seconds in a current browser. The calculator uses the choices of examples/b_5keV_si.toml (amorphous target at its tabulated density, ZBL screening, Lindhard–Scharff electronic stopping, 7° tilt), and a 15 eV displacement energy for a target element the element table gives none. It is not a replacement for the command line: it has no layers, compounds, crystals or electron mode.

Build it yourself

rustup target add wasm32-unknown-unknown
# wasm-bindgen command-line tool, release 0.2.129 (the version pinned in
# lindhard-wasm/Cargo.toml)
lindhard-wasm/build.sh web out/pkg
cp lindhard-wasm/web/index.html out/index.html
python3 -m http.server -d out        # then open http://localhost:8000

Agreement with the native build

The same input and seed give the same $R_p$ and $\Delta R_p$ as the native build, to within one standard error (in practice to about $10^{-15}$ relative): cargo test -p lindhard-wasm checks the native build and lindhard-wasm/tests/node/parity.test.mjs the WebAssembly build against one recorded result. The tolerance and its reason are in lindhard-wasm/tests/parity.rs: wasm32-unknown-unknown uses Rust’s bundled libm where a native build uses the platform’s, the two differ in the last bit, and a collision cascade amplifies that until individual histories diverge into statistically equivalent ones.