Quadrupole Splitting Distributions in Purpurite and Related Minerals

The quadrupole splitting distributions (QSDs) from the Mössbauer spectra of triphylite, ferrisicklerite and purpurite at 298 K and 80 K were obtained by the use of the Voigt-based quadrupole splitting distribution (QSD) method for the first time. QSDs of Fe²⁺ and Fe³⁺ are attributed to Fe²⁺ and Fe³⁺ at the corresponding octahedrally coordinated sites in the crystal structures of the three phosphate minerals. The influence on the distortion of the M2 site by different next-nearest neighbor (NNN) configurations was discussed based on the Jahn–Teller effect in purpurite, and the authors propose two M2 subsites with different distortions in purpurite. Two QSDs of Fe³⁺ in the Mössbauer spectra of purpurite are tentatively assigned to Fe³⁺ at the two M2 subsites, and next-nearest neighbor (NNN) effects were used to interpret the Mössbauer spectra of purpurite.