short communications
Density functional lattice dynamical calculations uncover the key role played by A-site elements with (n - 1)d10ns0 valence configurations (n = 5 and 6) in controlling the hexagonal-to-triclinic transformation in fluorapatites. The uniqueness of this site occupancy and chemistry was previously detected by data-driven methods, and the present study provides an electronic structure-based explanation of the prior informatics findings.