Refinement of monoclinic ReO2 structure from XRD by Rietveld method

Abstract

ReO 2 presents two crystalline variants, with monoclinic and orthorhombic structures. The former is metastable and irreversibly transforms to an orthorhombic structure above 460 o C. The structure of the latter was determined from studies on monocrystalline samples, whereas for the monoclinic variant there are no single crystals available so far. It was found only one monoclinic variant and the structure associated with this variant is based on studies on polycrystals. We analyzed a monoclinic oxide powder sample by X-ray diffraction and refined its pattern by means of the Rietveld Method. We obtained that the monoclinic variant belongs to space group P 21/c, with lattice parameters a = 5.615(3), b = 4.782(2), c = 5.574(2)Å, β = 120.13 (1) o .

Phase transitions in K-doped MoO2

“…For example, ReO 2 has a rutile-related structure (monoclinic, P2 1 /c) but shows an irreversible structural transition around 733 K to an orthorhombic phase in which both phases display metallic conductivity. 6 On the other hand, some of these oxides show metal-insulator transitions which are related to structural phase transitions from tetragonal to rutile-like structures. VO 2 and NbO 2 are some good examples for such transitions.…”

“…The refinement shows that the sample is single phase and belongs to the monoclinic structure with space group P2 1 /c which is similar to pure MoO 2 . The lattice parameters determined by Rietveld refinement were a ¼ 5.6082(3) Å , b ¼ 4.8589(9) Å , c ¼ 5.6264(5) Å , and b ¼ 120.929 (6) . In such refinement, the potassium atoms occupy the 2d interstitial Wyckoff position and the structure undergoes small deviations from the lattice parameters of the pattern for MoO 2 .…”

Structural Properties and Magnetic Ground States of 100 Binary d-Metal Oxides Studied by Hybrid Density Functional Methods

“…ReO 2 (oP12) crystallizes in an orthorhombic crystal structure with space group Pbcn (no. 60) [162]. The symmetry of the magnetically ordered structure is lowered to space group P2 1 2 1 2 (no.…”

“…ReO 2 (tP6) adopts tetragonal crystal structure with space group P4 2 /mnm (no. 136) [162,164,165]. The symmetry of the magnetically ordered structure is lowered to subgroup Cmmm (no.…”

CrxRe1−xO2oxides with different rutile-like structures: changes in the electronic configuration and resulting physical properties

“…[12], which has an antiferro-paramagnetic transition between 40 and 45 K. Ternary oxides in the system Cr-Re-O are less intensively investigated, although these systems offer an additional degree of freedom due to the ability of the Re ion to adopt formal oxidation states between +4 and +7 in complex oxides with different resulting properties. Both end members, CrO 2 [13] and the monoclinic modification of ReO 2 [14], have a rutile-like structure. A new modification of ReO 2 with rutile structure was also recently reported [15].…”