Gram–Charlier approach for anharmonic atomic displacements in inorganic solids: A review

Theuerdankite, Ag3AsO4, a new mineral from the Alter Theuerdank Mine, St. Andreasberg, Germany

“…We used a Wilson modification to the least-square routine (weights) to avoid the statistical bias (Wilson, 1976). We employed the third-order anharmonic Gram-Charlier development (see for instance Volkov et al, 2023) to describe the Debye-Waller factors for the Ag atoms, which improved the refinement considerably (see the Discussion). Refinement details are given in Table 4, atomic parameters (including atomic displacement parameters (ADP) and bond-valence sums calculated using parameters reported by Gagné and Hawthorne, 2015) are given in Table 5; the coefficients of the third -order Gram-Charlier development are given in crystallographic information file (cif); selected interatomic distances are reported in Table 6.…”