Synthesis, crystal structure and vibrational spectra of KCrV2O7 and RbCrV2O7

KCrV2O7 and RbCrV2O7 have been synthesized and their crystal structures have been determined using X-ray and neutron powder diffraction techniques. The phases crystallizes in space group P2/cP2/c with unit cell parameters for KCrV2O7: a=7.9526(1) Åa=7.9526(1) Å, b=4.87543(5) Åb=4.87543(5) Å, c=6.8910(1) Åc=6.8910(1) Å and β=101.162(1)°β=101.162(1)° and RbCrV2O7: a=8.2361(1) Åa=8.2361(1) Å, b=4.89480(4) Åb=4.89480(4) Å, c=6.8980(1) Åc=6.8980(1) Å and β=100.893(1)°β=100.893(1)°. The unit cell was confirmed by selected area electron diffraction studies. The crystal structure consists of two-dimensional CrV2O7− slabs parallel to the (100)-plane, formed from zigzag chains of face- and edge-sharing VO6 octahedra connected through CrO6-octahedra. The VO6 octahedra are very distorted including a short VO-vanadyl unit. The alkaline metal ions placed in the inter-slab space have coordination number 10+210+2 forming distorted triangular orthobicupolas. The infrared and Raman spectra of the compounds are presented and discussed.

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