Structural aspects of the metal–insulator transition in BaVS₃

Abstract

This study presents structural transitions of the one dimensional system BaVS 3 at low temperature by means of high resolution synchrotron powder diffraction. At room temperature the structure is hexagonal (P6 3 /mmc) with face sharing VS 6 octahedral chains along the c axis separated by Ba atoms leading to a V-V intrachain distance of 2.808(1)Å and an interchain distance 6.714(1)Å.The hexagonal structure at room temperature becomes orthorhombic (Cmc2 1 ) at 240K with a V straight chains transformed into uniform zigzag but without significant change in the electronic properties. At 70K a metal-insulator transition occurs with the appearance of a superstructure which doubles the chain periodicity. The structure refined at 40K revealed a weak monoclinic distorsion (b= 90.046(1)°) with 4 nonequivalent V sites. A valence bond analysis shows no evidence for charge disproportionation on these sites. However at 5K, the faces of the VS6 octahedra are stretched (site V1) or compressed (V3) inducing a 0.5e-charge disproportionation between the V1 and V3 sites. s8.m27.p1Towards an understanding of molecular crystals from powder X-ray diffraction techniques. With the advances of direct space strategies for structure solution from powder data [1,2], and in particular the success of the Genetic Algorithm method [3,4], a fundamental question on what structural information can be extracted from the diffraction data of increasingly poor diffraction data must be addressed. Structural problems which have the complexity of more than one molecule in the asymmetric unit present new challenges to powder X-ray diffraction [5], and recent developments in the structure solution of complicated structures using powder diffraction techniques will be highlighted [6].[1] Harris, K.D.M.; Tremayne, M.; Lightfoot, P.; Bruce, P.G.

Enhanced Electron Scattering upon Ion Relocation in BaVS3 at 69 K

“…Materials that bear the ABX structure are continuously studied due to their novel properties, which have potential applications, for example MOSFET (metal-oxide-semiconductor field-effect transistor) device fabrication [ 1 ]. One member of this family is barium vanadium sulfide (BaVS ), which has unique electronic properties such as metal-insulator transition [ 2 , 3 , 4 , 5 , 6 ], “bad metal” behavior [ 7 ], magnetic field induced structural transition [ 8 ], charge density waves (CDW) [ 5 ] and paramagnetic-antiferromagnetic phase transition [ 9 ]. It is experimentally [ 2 , 3 , 4 , 5 , 6 ] and theoretically [ 10 , 11 ] verified that the barium vanadium sulfide (BaVS ) has an orthorhombic to monoclinic structural transition during the metal-insulator (MI) phase transition at a temperature of approximately K. The given structural transition relates to an extensive regime of one-dimensional lattice fluctuations.…”