The crystal structure of Sr-hardystonite, Sr2ZnSi2O7

A synthetic strontium isomorph (Sr2ZnSi2O7) of the hardystonite structure (Ca2ZnSi2O7) was investigated with X-ray powder diffraction. The average structure (S.G. P-421m), a = 8.0007(1) Å, c = 5.1722(1) Å, was refined by Rietveld method and a RF2 = 0.0216 was achieved using 394 independent reflections. The results show that Sr-hardystonite has a melilite-type structure with no incommensurate modulations. Its geometrical and bonding features are consistent with trends defined by the other so-called normal and modulated melilite structures