Structural investigations of β-CaAlF5 by coupling powder XRD, NMR, EPR and spectroscopic parameter calculations

beta-CaAlF5 was synthesized by solid-state reaction. The precise structure was refined from X-ray powder diffraction data in the monoclinic space group P2(1)/c with lattice constants a = 5.3361 angstrom, b = 9.8298 angstrom, c = 7.3271 angstrom, and beta = 109.91 degrees (Z = 4). The structure exhibits isolated chains of AlF63- octahedra sharing opposite corners. F-19 and Al-27 solid state NMR spectra were recorded Using MAS and SATRAS techniques. An EPR spectrum was recorded for beta-CaAlF5:Cr3+. The experimental spectra were simulated in order to extract the NMR and EPR parameter values. Five fluorine sites and one low symmetry aluminium site were found in agreement with the refined structure. These parameters were calculated using empirical and ab-initio methods. The agreement obtained between the calculated F-19 chemical shift values, Al-27 quadrupolar parameters, Cr3+ EPR fine structure parameters and the experimental results demonstrates the complementarity of XRD, magnetic resonance experiments and theoretical methodologies. (C) 2005 Elsevier Inc. All rights reserved.