A pulsed NMR investigation of F chemical shift anisotropy in single crystals of fluorapatite

Measurement of the ¹⁹F NMR frequency versus orientation in single crystals of fluoropatite Ca₅F(PO₄)₃ about two perpendicular crystal axes has allowed determination of all principal components of the nuclear screening tensor, which was found to be axially symmetric with σ_∥ - σ_⊥ ≈ −84 ppm. An explanation of the negative value for σ_∥ - σ_⊥ is suggested by the bonding arrangement most consistent with the crystal structure.