Geometrical parameterization of the crystal chemistry of P63/m apatites: comparison with experimental data and ab initio results
Experimental single-crystal and Rietveld analysis results of apatite materials are compared with
ab initio simulations using a geometric crystal-chemical model involving 10 parameters and 4 constraints equivalent to unit-cell parameters (
a and
c) and 12 independent atom coordinates. From crystal-chemical parameters representing polyhedral distortions, the magnitude of
a and
c is reproduced to ±0.025Å accuracy whereas the
c/
a ratio is predicted to ±0.2%. Comparison of
ab initio optimized structures with experimental ones shows good agreement (within ±0.5–2.0%) with only the most reliable single-crystal refinements.
P. H. J. Mercier, Y. Le Page, P. S. Whitfield, L. D. Mitchell, I. J. Davidson and T. J. White
![[Model predictions]](https://www.iucr.org/__data/assets/image/0017/8144/actab.jpg)
Model predictions made from crystal-chemical parameters as a function of the observed c/a. Legend for symbols: red= single-crystal refinements; blue= ab initio optimizations.
