ENDF material data: element symbols, MAT numbers, and natural abundances.

A standalone, zero-dependency crate providing lookup tables for nuclear data:

• Element data: Symbols and names for Z=0 (neutron) through Z=118 (Oganesson)
• MAT numbers: ENDF material identifiers for 535 ground-state isotopes
• Natural abundances: IUPAC 2016 isotopic compositions for 289 isotopes
• ZA utilities: ENDF ZA encoding/decoding (ZA = Z×1000 + A)

All data is compiled into static arrays — no file I/O, no external dependencies.

Examples

// Element lookup
assert_eq!(endf_mat::element_symbol(92), Some("U"));
assert_eq!(endf_mat::symbol_to_z("Fe"), Some(26));

// MAT number lookup
assert_eq!(endf_mat::mat_number(92, 235), Some(9228));
assert_eq!(endf_mat::isotope_from_mat(9228), Some((92, 235)));

// Natural abundances
let u238 = endf_mat::natural_abundance(92, 238).unwrap();
assert!((u238 - 0.992742).abs() < 1e-6);

// ZA encoding
assert_eq!(endf_mat::za(92, 238), 92238);
assert_eq!(endf_mat::z_from_za(92238), 92);