Xpress: latest results from the new dedicated high pressure diffraction beamline at Elettra

With the recent opening of the Xpress beamline at the Elettra synchrotron radiation facility at Trieste, the high pressure (HP) diffraction community have yet another dedicated experimental set up at their disposal. Xpress is part of a scientific partnership between India and Italy under a project administered through the premier Indian scientific institute, the IISc Bangalore, comprising also a macromolecular x-ray diffraction beamline, the XRD2. Both beamlines utilize synchrotron radiation from a 49 poles, 3.6 Tesla superconducting wiggler, with Xpress employing the leftmost part of the wiggler fan to produce a 25 keV monochromatic x-ray beam focused on a large area MAR345 image plate detector. This is an optimal source for diffraction data acquisition in angle dispersive mode, ideally suited for in-situ HP measurements using diamond anvil cells (DACs). The beamline station is equipped with state of the art HP facilities involving DACs: high magnification long working distance microscope, precision microdriller, automatic pneumatic pressure controller, etc. A precision stage which can accommodate different types of DACs enables an easy switching between the pressure monitoring ruby fluorescence and the diffraction data collection using finite size (tens of microns in diameter) monochromatic x-ray beam. Figure 1 shows a recent photo of the end station of the Xpress beamline. Simplicity of the setup together with an efficient user friendly graphical user interface provides easiness in carrying out the user experiments. An in house developed cryogenic gas loader for Ar, N2, CO2, etc. a commercial He gas loading system, and a liquid nitrogen cryo stream based low temperature high pressure set up are currently in the advanced stage of commissioning. Very recently, in-situ HP single crystal (SC) diffraction measurements using DAC were successfully tested at the beamline; once further improvements will be implemented, HP-SC diffraction will be available for the users. We will present recent scientific highlights of the beamline activity performed on both powder and SC under HP. In particular, we discuss various examples of pressure-induced phase transitions on material systems, for example in FeGa3 [1] and in TlBiS2 [2] and signatures of pressure induced electronic topological transistions in IT-TiTe2 [3], CeP [4] and black phosphorus [5]. We also discuss pressure-induced amorphisation in A-site deficient La1/3NbO3 [6] and the possibility of material engnierring with pressure [7] in this system. Examples on synthesis of novel nanocomposites by pressure induced insertion and in-situ polymerization [8] will also be presented. Acknowledgments: B.J. acknowledges IISc Bangalore and ICTP Trieste for financial support through the award of the IISc-ICTP fellowship and Elettra Sincrotrone Trieste for support in participation of 2019 IUCr & ECA High Pressure Workshop. [1] G. R. Hearne et al., Phys. Rev. B 2018, 98, 020101. [2] V. Rajaji et al., Phys. Rev. B 2019, 99, 184109. [3] V. Rajaji et al., Phys. Rev. B 2018, 97, 085107. [4] B. Joseph et al., Phys. Chem. Chem. Phys. 2017, 19, 17526. [5] B. Joseph et al., J. Phys. Condens. Matter 2018, 30, 494002. [6] C. Marini et al., High Pressure Research 2017, 38, 12. [7] B. Joseph et al., (in proress) [8] F. Alabarse, et al., (in proress)