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The V 1−x Mo x O 2 phase diagram has high structural and electronic complexity that is driven by strong, short-range correlations that compete with the long-range rutile crystal structure. The substitution regime near 50% Mo occupancy is no exception, but there has so far been no significant progress in determining the actual structure. Reported here is a combined study using single crystal X-ray diffraction, powder X-ray diffraction, and representational analysis to examine both the local and crystallographically averaged atomic structures simultaneously near x = 0.50. Between about x = 0.50 and 0.60, the average structure of V 1−x Mo x O 2 is the parent rutile phase, but the local symmetry is broken by atomic displacements that are best described using the orthorhombic subgroup Fmmm . This model is locally similar to the two-dimensionally ordered 2D-M2 phase recently reported in the compositional range 0.19 ≤ x ≤ 0.30, except the correlation length is much shorter in the 2D plane, and longer in the frustrated one, making it more isotropic. This work also extends the 2D-M2 phase regime up to x = 0.43, and suggests that the local- Fmmm phase observed here can be seen as the end result of the continued suppression of the 2D-M2 phase through enhanced geometric frustration between the intrinsic order parameters. This suggests that other doped-rutile phases with elusive structures may also be dominated by similar short-range correlations that are hidden in the diffuse scattering. 

With NSF MRI support, we have recently purchased a dual source single crystal diffractometer equipped with a high resoln. detector.  The purpose of this presentation is to publicize the new instrument and we seek users in the Southeast to maximize the pos. impact of this instrument on research efforts in the Southeastern US.  Users at primarily undergraduate institutions and historically black colleges and universities are particularly encouraged to use this new resource.  In general, an X-ray diffractometer allows accurate and precise measurements of the full three-dimensional structure of a mol., including bond distances and angles, and provides accurate information about the spatial arrangement of a mol. relative to neighboring mols.  The studies described here impact many areas, including org. and inorg. chem., materials chem. and biochem.  This instrument is an integral part of teaching as well as research and research training of graduate and undergraduate students in chem. and biochem. at this institution and at partner institutions.  This poster will describe some examples of how the new diffractometer will enhance research in inorg. chem., materials chem. (via diffuse scattering), and biochem.