Rotation runs now estimate the standard uncertainties of the cell. Every strong integrated
observation (I > 3 sigma, unclipped, unsaturated, off ice rings) gives |q| = 1/d at its observed
centroid, which depends on the detector geometry only; q^2 = h^T G* h is linear in the reciprocal
metric, so the components of G* the point group leaves free (projected from the group's rotation
parts, any setting) are fitted by weighted linear least squares with 4-sigma rejection, and the
GoF-scaled covariance is carried analytically onto a, b, c, alpha, beta, gamma (ties give equal
e.s.d.s, fixed angles zero). Least-squares cell e.s.d.s are known to be too small (Herbstein 2000),
so the same fit is made on 8 blocks of consecutive frames and their scatter / sqrt(8) is the second
estimate; the written e.s.d. is the larger of the two per parameter. Stills get none.
Outputs: <prefix>.ins next to every .hkl (TITL, CELL at the wavelength, ZERR with Z = order of the
group, LATT/SYMM from the space group - positive LATT only with -1 at the origin - a placeholder
organic SFAC/UNIT at 18 A^3 per non-H atom, HKLF 4, END); the mmCIF gains _cell.*_esd ("." where
fixed) and _cell_measurement.reflns_used/theta_min/theta_max, and writes the cell to 4/3 decimals;
report keys CELL_ESD, CELL_ESD_LSQ, CELL_ESD_BLOCKS, CELL_ESD_BLOCK_COUNT, CELL_ESD_REFLECTIONS,
CELL_ESD_THETA_RANGE_DEG (+ dev CELL_ESD_OBSERVATIONS, CELL_DSPACING_FIT).
On 13 small-molecule sets the block scatter is 10-40x the least-squares e.s.d. and is what gets
written; it lands within ~0.3-5x of XDS's CORRECT.LP e.s.d.s. SHELXT solves from the generated
.ins and SHELXL carries ZERR into its CIF su. Costs 12 ms on a small molecule, 0.16 s on 690k
lysozyme observations.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015CeEGgpKdfkCTJb3YNMJcu
(cherry picked from commit e74a3be76261fe1b6c0ff7b80c21afc4768c46cd)
