STRUCTURE REFINEMENT OF TRICLINIC TUNGSTEN TRIOXIDE

The thermodynamically stable form of WO3 at room temperature is tricli nic. The structure of this form of WO3 was for the first time refined from neutron diffraction data. The data were obtained on a new high re solution powder diffractometer. The structure obtained appears to be s omewhat more accurate than that obtained from single crystal X-ray dif fraction data. Rietveld approach was used to refine the neutron powder diffraction data. Results using the software packages GSAS, Rietan an d PROFIL are compared. Using GSAS, an R(wp) of 7.97 and an R(p) of 5.8 7 were obtained. Neutron diffraction data were also collected and anal ysed on a sample which was a mixture of the monoclinic and triclinic f orms of WO3; Rietveld refinements of this data were stable and yielded reasonable results.