EPR theoretical study of local lattice structure on Mn2+ ion doped in calcite and differences between single crystal and fresh water snail, Pila globosa

By diagonalizing the complete energy matrices for a d5 configuration ion in a trigonal ligand-field and considering the second-order, fourth-order EPR parameters D and (a − F) simultaneously, the substitution position of Mn2+ ion in the CaCO3:Mn2+ system has been studied by analyzing the optical absorption and EPR spectra of single crystal and the ostracum layer of operculum of fresh water snail Pila globosa. The results show that in the single crystal there is an obvious compressed distortion ΔR = −0.158 Å and Δθ = 0.70°, and the distortion in P. globosa is ΔR = −0.107 Å and Δθ = −0.34° ∼ −0.23°. Meanwhile the EPR parameters 104(a − F) = 7.02–7.29 cm−1 and 104a = 6.35 cm−1 are predicted in P. globosa.