lindhard/

elements.rs

//! Element table, Z = 1..=92.
//!
//! The table is `const` data with no I/O, so table builders and a WASM front
//! end can use it directly. Provenance is also recorded in
//! `docs/data-provenance.md`.
//!
//! # Sources
//!
//! * **Atomic weight** (`atomic_weight`, g/mol, i.e. relative atomic mass):
//!   the CIAAW / IUPAC standard atomic weights as tabulated at
//!   <https://www.ciaaw.org/atomic-weights.htm> ("Standard Atomic Weights
//!   2024": the 2021 report, T. Prohaska et al., "Standard atomic weights of
//!   the elements 2021", Pure Appl. Chem. 94, 573 (2022),
//!   doi:10.1515/pac-2019-0603, plus the CIAAW 2024 revisions of Gd, Lu and
//!   Zr). For the 14 elements whose standard weight is an interval (H, Li, B,
//!   C, N, O, Mg, Si, S, Cl, Ar, Br, Tl, Pb) the single value is the
//!   abridged value of <https://www.ciaaw.org/abridged-atomic-weights.htm>,
//!   which the 2021 report (Table 1, column 7) says replaces, and equals, the
//!   former conventional atomic weights; for H that value is printed 1.0080,
//!   the former conventional 1.008. Elements with no standard atomic weight
//!   (Tc, Pm, Po, At, Rn, Fr, Ra, Ac) carry the mass number of their
//!   longest-lived isotope as listed by CIAAW at
//!   <https://www.ciaaw.org/radioactive-elements.htm> (from NUBASE2020,
//!   F. G. Kondev et al., Chin. Phys. C 45, 030001 (2021)) and have
//!   `weight_is_mass_number == true`; that is a convention, not a measurement
//!   of a natural mixture. For Tc that page lists 97 and 98 as equally
//!   long-lived; 98 is used. All 92 entries checked against these pages on
//!   2026-10-06 (#15).
//! * **Density** (`density_g_cm3`): density of the solid, g/cm³, as printed
//!   in A. Thompson et al., *X-Ray Data Booklet*, LBNL/PUB-490 Rev. 3
//!   (Lawrence Berkeley National Laboratory, October 2009), section 5.2,
//!   Table 5-2 "Properties of the elements", pp. 5-5 to 5-8
//!   (<https://xdb.lbl.gov/xdb-new.pdf>, PDF pages 153-156). Section 5.2 says
//!   the data were taken mostly from D. R. Lide (ed.), *CRC Handbook of
//!   Chemistry and Physics*, 80th ed. (CRC Press, 1999), and that densities
//!   are specific gravities at 20 °C unless a superscript gives another
//!   temperature (25 °C for Si, Sc, Ni, Zn, Ge, Y, La, Ce, Nd, Pm, Sm, Eu,
//!   Gd, Dy, Ho, Er, Tm, Lu; V 18.7 °C, Ga 29.6 °C, Ir 17 °C). Tc and Pa are
//!   marked "calculated" there, U "~18.95". The table names no allotrope
//!   except graphite for C. All populated entries checked on 2026-10-07
//!   (#15; the PDF's SHA-256 is recorded in `docs/data-provenance.md`), and
//!   37 values set to the printed ones. Four entries the booklet does not pin
//!   were checked on 2026-10-07 (#15) against other open primary
//!   compilations, all U.S. government reports:
//!   - Cr 7.20 (was 7.15, which lay **outside** the booklet's printed range
//!     7.18-7.20): the upper end of that range, and the density "calculated
//!     from the NBS lattice constant", 7.200 at 25 °C, in H. E. Swanson,
//!     R. K. Fuyat and G. M. Ugrinic, *Standard X-ray Diffraction Powder
//!     Patterns*, NBS Circular 539, Vol. V (1955), p. 20
//!     (<https://nvlpubs.nist.gov/nistpubs/Legacy/circ/nbscircular539v5.pdf>).
//!     This is an X-ray (crystal) density.
//!   - Au 19.30: the booklet prints "~19.3"; NBS Circular 539, Vol. I
//!     (Swanson and Tatge, 1953), p. 33, prints 19.302 at 25 °C from its
//!     lattice constant
//!     (<https://nvlpubs.nist.gov/nistpubs/Legacy/circ/nbscircular539v1.pdf>).
//!   - Ra 5.0: no density in the booklet; "a specific gravity of
//!     approximately 5.0" in H. W. Kirby and M. L. Salutsky, *The
//!     Radiochemistry of Radium*, NAS-NS 3057 (1964), p. 3, citing the
//!     International Critical Tables (<https://www.osti.gov/servlets/purl/4560824>).
//!   - Ac 10.07: no density in the booklet; the crystal density of fcc Ac
//!     metal (a = 5.311 Å), Table 4, p. 11, of J. D. Farr, A. L. Giorgi,
//!     M. G. Bowman and R. K. Money, "The crystal structure of actinium metal
//!     and actinium hydride", Los Alamos report LA-1545 (1953)
//!     (<https://www.osti.gov/servlets/purl/4397640>), published as
//!     J. Inorg. Nucl. Chem. 18, 42 (1961).
//!
//!   Still **not verified** to their stored digits: C 2.267 (printed as the
//!   range 1.9-2.3) and Mn 7.44 (the upper end of the printed range
//!   7.21-7.44). For Mn, the X-ray density of alpha-Mn, "(calculated) 7.475
//!   g/cm³" at 25 °C (a = 8.9121 Å, Z = 58), is printed in M. C. Morris
//!   et al., *Standard X-ray Diffraction Powder Patterns*, NBS Monograph 25,
//!   Section 17 (1980), p. 50
//!   (<https://nvlpubs.nist.gov/nistpubs/Legacy/MONO/nbsmonograph25-17.pdf>,
//!   checked 2026-10-07, #15). It lies above the booklet's range, so unlike
//!   Cr it does not pin a value inside that range; 7.44 is kept, unverified.
//!   Si keeps 2.329: the booklet prints 2.33
//!   at 25 °C, and 2.329 is the crystal density `M(Si) / V_m(Si)` from the
//!   CODATA 2022 "molar volume of silicon" (1.205 883 199e-5 m³/mol,
//!   <https://physics.nist.gov/cuu/Constants/Table/allascii.txt>) for any
//!   weight in the standard interval [28.084, 28.086]. The specific gravities
//!   are used as g/cm³; the booklet does not state the reference water
//!   state. Later CRC editions may differ; none was seen. It is `None` where
//!   no solid density at ambient conditions exists (gases: H, He, N, O, F,
//!   Ne, Cl, Ar, Kr, Xe, Rn; liquids: Br, Hg; no data: At, Fr). Densities are
//!   a default for a pure element only; compounds need an explicit density
//!   override.
//! * **Sublimation (cohesive) enthalpy** (`default_surface_binding_ev`): where
//!   a measured value is tabulated, the cohesive energy per atom (eV) of
//!   C. Kittel, *Introduction to Solid State Physics*, 8th ed. (Wiley, 2005),
//!   chapter 3 (cohesive energies of the elements), which is the enthalpy of
//!   atomization at 0 K. Using it as the surface binding energy `E_s` is the
//!   usual binary-collision convention (Sigmund, Phys. Rev. 184, 383 (1969)),
//!   **not** a measured surface barrier. Elements left `None` must have
//!   `E_s` set explicitly by the user rather than have one invented.
//!   **Verified** on 2026-10-07 (#15) against Table 1 "Cohesive energies",
//!   chapter 3, p. 50 of the 8th edition (Wiley, 2005, ISBN 0-471-41526-X;
//!   edition, publisher and ISBN read from the title and copyright pages of
//!   the copy used, see `docs/data-provenance.md`). The table prints each
//!   element in kJ/mol, eV/atom and kcal/mol ("energy required to form
//!   separated neutral atoms in their ground electronic state from the solid
//!   at 0 K at 1 atm. The data were supplied by Prof. Leo Brewer."); the
//!   eV/atom value is used, to the digits printed. All 35 populated entries
//!   were compared: 33 equal the printed value, and Na (was 1.11) and K (was
//!   0.93) were set to the printed 1.113 and 0.934. The table also prints
//!   values for elements left `None` here (among them N, O, P, S, Sc, Mn,
//!   Se, the rare gases and most lanthanides and actinides); those defaults
//!   stay unset, since #15 audits the populated entries only. Earlier
//!   cross-check, kept as a test: L. Brewer, "The cohesive energies of the
//!   elements", report LBL-3720 (1975), Table I, kcal/gram-atom
//!   (<https://www.osti.gov/servlets/purl/7187973>).
//! * **Displacement energy** (`default_displacement_ev`): threshold
//!   displacement energies as recommended in ASTM E521 ("Standard Practice for
//!   Investigating the Effects of Neutron Radiation Damage Using Charged-Particle
//!   Irradiation"), the convention underlying the NRT damage model
//!   (Norgett, Robinson, Torrens, Nucl. Eng. Des. 33, 50 (1975)). These are
//!   conventions for damage accounting, not measured properties of a specific
//!   crystal direction. `None` where no convention value is recorded.
//!   **Not verified**: the standard could not be reached (see
//!   `docs/data-provenance.md`). The values are also not those of the
//!   Greenwood-Smither compilation used by SPECTER and NJOY (they differ for
//!   Al, Ti, Cu, Nb and Ag), which is not E521 either.

/// One element of the periodic table with its default data.
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct Element {
    /// Atomic number.
    pub z: u8,
    /// Element symbol, e.g. `"Si"`.
    pub symbol: &'static str,
    /// Standard (conventional) atomic weight in g/mol; see the module docs.
    pub atomic_weight: f64,
    /// True if `atomic_weight` is the mass number of the longest-lived isotope
    /// because IUPAC publishes no standard atomic weight for the element.
    pub weight_is_mass_number: bool,
    /// Default solid density in g/cm³, if one is defined; see the module docs.
    pub density_g_cm3: Option<f64>,
    /// Default surface binding energy `E_s` in eV (cohesive-energy convention).
    pub default_surface_binding_ev: Option<f64>,
    /// Default displacement energy `E_d` in eV (ASTM E521 convention).
    pub default_displacement_ev: Option<f64>,
}

impl Element {
    /// Atomic mass in kg: `atomic_weight` times the atomic mass constant.
    ///
    /// (The molar-mass constant differs from 1 g/mol by about 1e-9, CODATA
    /// 2022 `M_u` = 1.000 000 001 05e-3 kg/mol; the standard-atomic-weight
    /// uncertainty is far larger.)
    pub fn mass_kg(&self) -> f64 {
        self.atomic_weight * crate::constants::ATOMIC_MASS_UNIT
    }

    /// Default density in kg/m³, if defined.
    pub fn density_kg_m3(&self) -> Option<f64> {
        self.density_g_cm3.map(crate::units::g_cm3_to_kg_m3)
    }
}

/// Number of elements in the table.
pub const NUM_ELEMENTS: usize = 92;

/// Look an element up by atomic number (1..=92).
pub fn element(z: u8) -> Option<&'static Element> {
    if z == 0 {
        return None;
    }
    ELEMENTS.get(usize::from(z) - 1)
}

/// Look an element up by case-sensitive symbol (`"Si"`, not `"si"`).
pub fn element_by_symbol(symbol: &str) -> Option<&'static Element> {
    ELEMENTS.iter().find(|e| e.symbol == symbol)
}

const fn el(
    z: u8,
    symbol: &'static str,
    atomic_weight: f64,
    weight_is_mass_number: bool,
    density_g_cm3: Option<f64>,
    default_surface_binding_ev: Option<f64>,
    default_displacement_ev: Option<f64>,
) -> Element {
    Element {
        z,
        symbol,
        atomic_weight,
        weight_is_mass_number,
        density_g_cm3,
        default_surface_binding_ev,
        default_displacement_ev,
    }
}

/// The table, indexed by `Z - 1`.
// Sn's cohesive energy (3.14 eV) is data, not pi.
#[allow(clippy::approx_constant)]
pub static ELEMENTS: [Element; NUM_ELEMENTS] = [
    el(1, "H", 1.008, false, None, None, None),
    el(2, "He", 4.002602, false, None, None, None),
    el(3, "Li", 6.94, false, Some(0.534), Some(1.63), None),
    el(4, "Be", 9.0121831, false, Some(1.848), Some(3.32), None),
    el(5, "B", 10.81, false, Some(2.34), Some(5.81), None),
    el(6, "C", 12.011, false, Some(2.267), Some(7.37), None),
    el(7, "N", 14.007, false, None, None, None),
    el(8, "O", 15.999, false, None, None, None),
    el(9, "F", 18.998403162, false, None, None, None),
    el(10, "Ne", 20.1797, false, None, None, None),
    el(11, "Na", 22.98976928, false, Some(0.971), Some(1.113), None),
    el(12, "Mg", 24.305, false, Some(1.738), Some(1.51), None),
    el(
        13,
        "Al",
        26.9815384,
        false,
        Some(2.6989),
        Some(3.39),
        Some(25.0),
    ),
    el(14, "Si", 28.085, false, Some(2.329), Some(4.63), None),
    el(15, "P", 30.973761998, false, Some(1.82), None, None),
    el(16, "S", 32.06, false, Some(2.07), None, None),
    el(17, "Cl", 35.45, false, None, None, None),
    el(18, "Ar", 39.95, false, None, None, None),
    el(19, "K", 39.0983, false, Some(0.862), Some(0.934), None),
    el(20, "Ca", 40.078, false, Some(1.55), Some(1.84), None),
    el(21, "Sc", 44.955907, false, Some(2.989), None, None),
    el(22, "Ti", 47.867, false, Some(4.54), Some(4.85), Some(30.0)),
    el(23, "V", 50.9415, false, Some(6.11), Some(5.31), Some(40.0)),
    el(24, "Cr", 51.9961, false, Some(7.20), Some(4.1), Some(40.0)),
    el(25, "Mn", 54.938043, false, Some(7.44), None, None),
    el(26, "Fe", 55.845, false, Some(7.874), Some(4.28), Some(40.0)),
    el(
        27,
        "Co",
        58.933194,
        false,
        Some(8.90),
        Some(4.39),
        Some(40.0),
    ),
    el(
        28,
        "Ni",
        58.6934,
        false,
        Some(8.902),
        Some(4.44),
        Some(40.0),
    ),
    el(29, "Cu", 63.546, false, Some(8.96), Some(3.49), Some(30.0)),
    el(30, "Zn", 65.38, false, Some(7.133), Some(1.35), None),
    el(31, "Ga", 69.723, false, Some(5.904), Some(2.81), None),
    el(32, "Ge", 72.630, false, Some(5.323), Some(3.85), None),
    el(33, "As", 74.921595, false, Some(5.73), Some(2.96), None),
    el(34, "Se", 78.971, false, Some(4.79), None, None),
    el(35, "Br", 79.904, false, None, None, None),
    el(36, "Kr", 83.798, false, None, None, None),
    el(37, "Rb", 85.4678, false, Some(1.532), None, None),
    el(38, "Sr", 87.62, false, Some(2.54), None, None),
    el(39, "Y", 88.905838, false, Some(4.469), None, None),
    el(40, "Zr", 91.222, false, Some(6.506), Some(6.25), Some(40.0)),
    el(
        41,
        "Nb",
        92.90637,
        false,
        Some(8.57),
        Some(7.57),
        Some(60.0),
    ),
    el(42, "Mo", 95.95, false, Some(10.22), Some(6.82), Some(60.0)),
    el(43, "Tc", 98.0, true, Some(11.50), None, None),
    el(44, "Ru", 101.07, false, Some(12.41), None, None),
    el(45, "Rh", 102.90549, false, Some(12.41), None, None),
    el(46, "Pd", 106.42, false, Some(12.02), Some(3.89), None),
    el(
        47,
        "Ag",
        107.8682,
        false,
        Some(10.50),
        Some(2.95),
        Some(30.0),
    ),
    el(48, "Cd", 112.414, false, Some(8.65), Some(1.16), None),
    el(49, "In", 114.818, false, Some(7.31), Some(2.52), None),
    el(50, "Sn", 118.710, false, Some(7.31), Some(3.14), None),
    el(51, "Sb", 121.760, false, Some(6.691), Some(2.75), None),
    el(52, "Te", 127.60, false, Some(6.24), None, None),
    el(53, "I", 126.90447, false, Some(4.93), None, None),
    el(54, "Xe", 131.293, false, None, None, None),
    el(55, "Cs", 132.90545196, false, Some(1.873), None, None),
    el(56, "Ba", 137.327, false, Some(3.5), None, None),
    el(57, "La", 138.90547, false, Some(6.145), None, None),
    el(58, "Ce", 140.116, false, Some(6.770), None, None),
    el(59, "Pr", 140.90766, false, Some(6.773), None, None),
    el(60, "Nd", 144.242, false, Some(7.008), None, None),
    el(61, "Pm", 145.0, true, Some(7.264), None, None),
    el(62, "Sm", 150.36, false, Some(7.52), None, None),
    el(63, "Eu", 151.964, false, Some(5.244), None, None),
    el(64, "Gd", 157.249, false, Some(7.901), None, None),
    el(65, "Tb", 158.925354, false, Some(8.23), None, None),
    el(66, "Dy", 162.500, false, Some(8.551), None, None),
    el(67, "Ho", 164.930329, false, Some(8.795), None, None),
    el(68, "Er", 167.259, false, Some(9.066), None, None),
    el(69, "Tm", 168.934219, false, Some(9.321), None, None),
    el(70, "Yb", 173.045, false, Some(6.966), None, None),
    el(71, "Lu", 174.96669, false, Some(9.841), None, None),
    el(72, "Hf", 178.486, false, Some(13.31), None, None),
    el(
        73,
        "Ta",
        180.94788,
        false,
        Some(16.654),
        Some(8.1),
        Some(90.0),
    ),
    el(74, "W", 183.84, false, Some(19.3), Some(8.9), Some(90.0)),
    el(75, "Re", 186.207, false, Some(21.02), None, None),
    el(76, "Os", 190.23, false, Some(22.57), None, None),
    el(77, "Ir", 192.217, false, Some(22.42), None, None),
    el(78, "Pt", 195.084, false, Some(21.45), Some(5.84), None),
    el(
        79,
        "Au",
        196.966570,
        false,
        Some(19.30),
        Some(3.81),
        Some(30.0),
    ),
    el(80, "Hg", 200.592, false, None, None, None),
    el(81, "Tl", 204.38, false, Some(11.85), None, None),
    el(82, "Pb", 207.2, false, Some(11.35), Some(2.03), Some(25.0)),
    el(83, "Bi", 208.98040, false, Some(9.747), None, None),
    el(84, "Po", 209.0, true, Some(9.32), None, None),
    el(85, "At", 210.0, true, None, None, None),
    el(86, "Rn", 222.0, true, None, None, None),
    el(87, "Fr", 223.0, true, None, None, None),
    el(88, "Ra", 226.0, true, Some(5.0), None, None),
    el(89, "Ac", 227.0, true, Some(10.07), None, None),
    el(90, "Th", 232.0377, false, Some(11.72), None, None),
    el(91, "Pa", 231.03588, false, Some(15.37), None, None),
    el(92, "U", 238.02891, false, Some(18.95), None, None),
];

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn table_is_ordered_and_complete() {
        for (i, e) in ELEMENTS.iter().enumerate() {
            assert_eq!(usize::from(e.z), i + 1);
            assert!(e.atomic_weight > 0.9);
            if let Some(d) = e.density_g_cm3 {
                assert!(d > 0.0 && d < 30.0);
            }
        }
        assert_eq!(element(14).unwrap().symbol, "Si");
        assert_eq!(element(92).unwrap().symbol, "U");
        assert!(element(0).is_none() && element(93).is_none());
        assert_eq!(element_by_symbol("Ga").unwrap().z, 31);
        assert!(element_by_symbol("Xx").is_none());
    }

    #[test]
    fn mass_number_flag_is_exactly_the_elements_without_standard_weight() {
        // Tc, Pm, Po, At, Rn, Fr, Ra, Ac have no CIAAW standard atomic weight.
        let flagged: Vec<u8> = ELEMENTS
            .iter()
            .filter(|e| e.weight_is_mass_number)
            .map(|e| e.z)
            .collect();
        assert_eq!(flagged, [43, 61, 84, 85, 86, 87, 88, 89]);
        // A mass number is an integer.
        for e in ELEMENTS.iter().filter(|e| e.weight_is_mass_number) {
            assert_eq!(e.atomic_weight, e.atomic_weight.trunc());
        }
    }

    #[test]
    fn symbols_are_unique() {
        for (i, a) in ELEMENTS.iter().enumerate() {
            for b in &ELEMENTS[i + 1..] {
                assert_ne!(a.symbol, b.symbol);
            }
        }
    }

    fn by(symbol: &str) -> &'static Element {
        element_by_symbol(symbol).unwrap()
    }

    /// Standard atomic weights as printed by CIAAW, "Standard Atomic Weights
    /// 2024", <https://www.ciaaw.org/atomic-weights.htm> (read 2026-10-06),
    /// to the digits printed there. For interval elements the value is the
    /// conventional (abridged) one of
    /// <https://www.ciaaw.org/abridged-atomic-weights.htm>. That value need
    /// not lie inside the interval (O: 15.999 against [15.999 03, 15.999 77]);
    /// the 2021 report (Prohaska et al. 2022, text above Table 1) defines its
    /// printed uncertainty as the smallest symmetric one covering the
    /// interval, so the check is `value +- uncertainty` contains the interval.
    #[test]
    fn atomic_weights_match_ciaaw_spot_values() {
        // Single-valued standard weights, value(uncertainty) as printed.
        for (sym, w) in [
            ("P", 30.973_761_998), // 30.973 761 998(5)
            ("Ga", 69.723),        // 69.723(1)
            ("As", 74.921_595),    // 74.921 595(6)
            ("Au", 196.966_570),   // 196.966 570(4)
            // Corrected in #15 (were 44.955908, 88.90584, 91.224, 157.25, 174.9668).
            ("Sc", 44.955_907), // 44.955 907(4)
            ("Y", 88.905_838),  // 88.905 838(2)
            ("Zr", 91.222),     // 91.222(3), CIAAW 2024 revision
            ("Gd", 157.249),    // 157.249(2), CIAAW 2024 revision
            ("Lu", 174.966_69), // 174.966 69(5), CIAAW 2024 revision
        ] {
            assert_eq!(by(sym).atomic_weight, w, "{sym}");
            assert!(!by(sym).weight_is_mass_number, "{sym}");
        }
        // Interval elements: (conventional value +- its abridged uncertainty,
        // standard-weight interval).
        for (sym, w, u, lo, hi) in [
            ("Si", 28.085, 0.001, 28.084, 28.086),
            ("O", 15.999, 0.001, 15.999_03, 15.999_77),
            ("B", 10.81, 0.02, 10.806, 10.821),
            ("Ar", 39.95, 0.16, 39.792, 39.963),
            ("Pb", 207.2, 1.1, 206.14, 207.94),
        ] {
            let e = by(sym);
            assert_eq!(e.atomic_weight, w, "{sym}");
            assert!(w - u <= lo && hi <= w + u, "{sym}");
            assert!(!e.weight_is_mass_number, "{sym}");
        }
    }

    /// Mass numbers of the longest-lived isotopes, CIAAW "Radioactive
    /// elements", <https://www.ciaaw.org/radioactive-elements.htm> (NUBASE2020;
    /// read 2026-10-06). Tc is listed with 97 and 98 as equally long-lived.
    #[test]
    fn mass_number_fallbacks_match_ciaaw() {
        for (sym, a) in [
            ("Tc", 98.0),
            ("Pm", 145.0),
            ("Po", 209.0),
            ("At", 210.0),
            ("Rn", 222.0),
            ("Fr", 223.0),
            ("Ra", 226.0),
            ("Ac", 227.0),
        ] {
            assert_eq!(by(sym).atomic_weight, a, "{sym}");
            assert!(by(sym).weight_is_mass_number, "{sym}");
        }
    }

    /// `E_s` against the cited source: C. Kittel, *Introduction to Solid State
    /// Physics*, 8th ed. (Wiley, 2005), ch. 3, Table 1 "Cohesive energies",
    /// p. 50, eV/atom row, to the digits printed (read 2026-10-07, #15).
    /// Every populated entry is listed, so a new or changed default fails
    /// here until it is checked against the table.
    #[test]
    // Sn's cohesive energy (3.14 eV) is data, not pi.
    #[allow(clippy::approx_constant)]
    fn surface_binding_matches_kittel_8th_ed_table_1() {
        let kittel: [(&str, f64); 35] = [
            ("Li", 1.63),
            ("Be", 3.32),
            ("B", 5.81),
            ("C", 7.37),
            ("Na", 1.113), // corrected in #15 (was 1.11)
            ("Mg", 1.51),
            ("Al", 3.39),
            ("Si", 4.63),
            ("K", 0.934), // corrected in #15 (was 0.93)
            ("Ca", 1.84),
            ("Ti", 4.85),
            ("V", 5.31),
            ("Cr", 4.10),
            ("Fe", 4.28),
            ("Co", 4.39),
            ("Ni", 4.44),
            ("Cu", 3.49),
            ("Zn", 1.35),
            ("Ga", 2.81),
            ("Ge", 3.85),
            ("As", 2.96),
            ("Zr", 6.25),
            ("Nb", 7.57),
            ("Mo", 6.82),
            ("Pd", 3.89),
            ("Ag", 2.95),
            ("Cd", 1.16),
            ("In", 2.52),
            ("Sn", 3.14),
            ("Sb", 2.75),
            ("Ta", 8.10),
            ("W", 8.90),
            ("Pt", 5.84),
            ("Au", 3.81),
            ("Pb", 2.03),
        ];
        for (sym, ev) in kittel {
            assert_eq!(by(sym).default_surface_binding_ev, Some(ev), "{sym}");
        }
        let populated = ELEMENTS
            .iter()
            .filter(|e| e.default_surface_binding_ev.is_some())
            .count();
        assert_eq!(populated, kittel.len());
        // Kittel prints O 2.60 and P 3.43 eV/atom, but these defaults are
        // unset by design (#15 audits populated entries only); the user sets
        // E_s for them.
        assert_eq!(by("O").default_surface_binding_ev, None);
        assert_eq!(by("P").default_surface_binding_ev, None);
    }

    /// Cross-check of `E_s` against L. Brewer, LBL-3720 (1975), Table I,
    /// atomization energy to the gaseous ground state at 0 K, kcal/gram-atom
    /// (<https://www.osti.gov/servlets/purl/7187973>), a second source
    /// beside the cited Kittel table (whose data Brewer supplied).
    /// 1 kcal/mol = 4184 J / (e N_A) eV per atom (thermochemical calorie).
    #[test]
    fn surface_binding_cross_checks_against_brewer_lbl_3720() {
        use crate::constants::{AVOGADRO, ELEMENTARY_CHARGE};
        let kcal_ev = 4184.0 / (ELEMENTARY_CHARGE * AVOGADRO);
        // Agree to the printed digit (half a unit in the last place, 0.005 eV).
        for (sym, kcal) in [("Si", 106.7), ("Ga", 64.8), ("As", 68.2), ("Au", 87.96)] {
            let es = by(sym).default_surface_binding_ev.unwrap();
            assert!(
                (es - kcal * kcal_ev).abs() <= 0.005,
                "{sym}: {es} vs {}",
                kcal * kcal_ev
            );
        }
        // B (beta): Brewer 133 +- 3 kcal = 5.77 +- 0.13 eV; the stored 5.81 is
        // Kittel's printed value (Table 1 also prints 134 kcal/mol for B),
        // inside Brewer's uncertainty.
        let b = by("B").default_surface_binding_ev.unwrap();
        assert!((b - 133.0 * kcal_ev).abs() <= 3.0 * kcal_ev, "{b}");
    }

    /// Densities as printed in the X-Ray Data Booklet, LBNL/PUB-490 Rev. 3
    /// (2009), Table 5-2, pp. 5-5 to 5-8 (<https://xdb.lbl.gov/xdb-new.pdf>,
    /// read 2026-10-07; from the CRC Handbook, 80th ed.), g/cm³, to the
    /// digits printed there. Superscripts give the temperature where it is
    /// not 20 °C.
    #[test]
    fn densities_match_x_ray_data_booklet_spot_values() {
        for (sym, rho) in [
            ("B", 2.34),
            ("P", 1.82),
            ("Ga", 5.904), // 5.904^29.6
            ("Cu", 8.96),
            ("Sc", 2.989), // 2.989^25; reviewer-flagged, unchanged
            // Corrected in #15 (were 5.727, 10.49, 1.93, 22.59, 19.1).
            ("As", 5.73),
            ("Ag", 10.50),
            ("Cs", 1.873),
            ("Os", 22.57),
            ("U", 18.95), // printed "~18.95"
        ] {
            assert_eq!(by(sym).density_g_cm3, Some(rho), "{sym}");
        }
        // Au is printed only as "~19.3"; the stored 19.30 agrees to that
        // precision, its second decimal is not verified.
        let au = by("Au").density_g_cm3.unwrap();
        assert!((au - 19.3).abs() < 0.05, "{au}");
    }

    /// Densities the X-Ray Data Booklet does not pin, checked against other
    /// open primary compilations (read 2026-10-07; see the module docs and
    /// `docs/data-provenance.md`), g/cm³.
    #[test]
    fn densities_match_other_primary_compilations() {
        // NBS Circular 539 Vol. I (1953), p. 33: Au 19.302 at 25 °C from the
        // lattice constant; the booklet prints "~19.3". Agrees to the stored
        // digits.
        let au = by("Au").density_g_cm3.unwrap();
        assert!((au - 19.302).abs() < 0.005, "{au}");
        // NBS Circular 539 Vol. V (1955), p. 20: Cr 7.200 at 25 °C from the
        // lattice constant, the upper end of the booklet's 7.18-7.20.
        // Corrected in #15 (was 7.15, outside that range).
        let cr = by("Cr").density_g_cm3.unwrap();
        assert_eq!(cr, 7.20);
        assert!((7.18..=7.20).contains(&cr));
        // Kirby and Salutsky, NAS-NS 3057 (1964), p. 3: Ra "approximately
        // 5.0". Reviewer-flagged; unchanged.
        assert_eq!(by("Ra").density_g_cm3, Some(5.0));
        // Farr et al., LA-1545 (1953), Table 4: Ac 10.07 (fcc, a = 5.311 Å).
        assert_eq!(by("Ac").density_g_cm3, Some(10.07));
    }

    /// The Ac entry is the crystal density of its fcc cell as LA-1545 prints
    /// it: 4 atoms of mass number 227 in a cube of edge 5.311 Å, rounded to
    /// the printed 10.07 g/cm³ (the report's a carries +- 0.010 Å).
    #[test]
    fn actinium_density_matches_its_lattice_constant() {
        use crate::constants::AVOGADRO;
        let ac = by("Ac");
        let a_cm = 5.311e-8;
        let rho = 4.0 * ac.atomic_weight / (AVOGADRO * a_cm * a_cm * a_cm);
        assert!((rho - ac.density_g_cm3.unwrap()).abs() < 0.01, "{rho}");
    }

    /// Mn is not pinned by any source read so far. The X-Ray Data Booklet
    /// prints the range 7.21-7.44; NBS Monograph 25, Section 17 (1980), p. 50,
    /// prints the alpha-Mn X-ray density "(calculated) 7.475 g/cm³" at 25 °C
    /// from a = 8.9121 Å and Z = 58 atoms per cell (volume printed as
    /// 707.85 ų). That page is reproduced here from its printed lattice
    /// constant with CODATA 2022 N_A and the CIAAW weight; it lies above the
    /// booklet's range, so the stored upper end, 7.44, is kept and stays
    /// unverified.
    #[test]
    fn manganese_density_is_bounded_but_not_pinned() {
        use crate::constants::AVOGADRO;
        let mn = by("Mn");
        let a_cm: f64 = 8.9121e-8;
        assert!((a_cm * a_cm * a_cm * 1e24 - 707.85).abs() < 0.005);
        let rho_x = 58.0 * mn.atomic_weight / (AVOGADRO * a_cm * a_cm * a_cm);
        assert!((rho_x - 7.475).abs() < 0.0005, "{rho_x}");
        let stored = mn.density_g_cm3.unwrap();
        assert_eq!(stored, 7.44);
        assert!((7.21..=7.44).contains(&stored));
        assert!(rho_x > 7.44);
    }

    /// Si: the CODATA 2022 "molar volume of silicon", V_m(Si) =
    /// 1.205 883 199e-5 m³/mol
    /// (<https://physics.nist.gov/cuu/Constants/Table/allascii.txt>), which
    /// equals N_A a³ / 8 for the listed lattice parameter a = 5.431 020 511e-10
    /// m, gives the crystal density M(Si) / V_m(Si). For every weight in the
    /// CIAAW standard interval [28.084, 28.086] it rounds to the stored 2.329
    /// g/cm³; the X-Ray Data Booklet prints 2.33 at 25 °C.
    #[test]
    fn silicon_density_matches_codata_molar_volume() {
        use crate::constants::AVOGADRO;
        let a = 5.431_020_511e-10; // m
        let v_m = 1.205_883_199e-5; // m^3/mol
        assert!((AVOGADRO * a * a * a / 8.0 / v_m - 1.0).abs() < 1e-9);
        let si = by("Si").density_g_cm3.unwrap();
        assert_eq!(si, 2.329);
        for m_g in [28.084, 28.085, 28.086] {
            // g/mol / (m^3/mol) = g/m^3; 1e-6 converts to g/cm^3.
            let rho = m_g / v_m * 1e-6;
            assert!((rho - si).abs() < 0.0005, "{m_g}: {rho}");
        }
        assert!((si - 2.33).abs() < 0.005);
    }

    /// Defaults that are unset by design stay unset. `E_d` values are not
    /// pinned: ASTM E521 could not be reached, so no populated value is
    /// source-verified.
    #[test]
    fn unset_defaults_are_preserved() {
        // Gases have no solid density.
        for sym in ["H", "N", "O", "F", "Cl", "Ar", "Rn"] {
            assert_eq!(by(sym).density_g_cm3, None, "{sym}");
        }
        // No E_d convention value is recorded for the semiconductor and dopant
        // elements; the user must set one.
        for sym in ["Si", "O", "Ga", "As", "B", "P"] {
            assert_eq!(by(sym).default_displacement_ev, None, "{sym}");
        }
    }
}