11 research outputs found
First Principles NMR Study of Fluorapatite under Pressure
NMR is the technique of election to probe the local properties of materials.
Herein we present the results of density functional theory (DFT) \textit{ab
initio} calculations of the NMR parameters for fluorapatite (FAp), a calcium
orthophosphate mineral belonging to the apatite family, by using the GIPAW
method [Pickard and Mauri, 2001]. Understanding the local effects of pressure
on apatites is particularly relevant because of their important role in many
solid state and biomedical applications. Apatites are open structures, which
can undergo complex anisotropic deformations, and the response of NMR can
elucidate the microscopic changes induced by an applied pressure. The computed
NMR parameters proved to be in good agreement with the available experimental
data. The structural evaluation of the material behavior under hydrostatic
pressure (from --5 to +100 kbar) indicated a shrinkage of the diameter of the
apatitic channel, and a strong correlation between NMR shielding and pressure,
proving the sensitivity of this technique to even small changes in the chemical
environment around the nuclei. This theoretical approach allows the exploration
of all the different nuclei composing the material, thus providing a very
useful guidance in the interpretation of experimental results, particularly
valuable for the more challenging nuclei such as Ca and O.Comment: 8 pages, 2 figures, 3 table