Sodium X-Ray Diffraction in the High-Pressure Regime

Transcription

1 Sodium X-Ray Diffraction in the High-Pressure Regime 2000 Liquid Liquid Isentrope hp4 Temperature (K) bcc Melting curve fcc mp512 o120 ti50 ap90 ti19 X. Gong University of Rochester Laboratory for Laser Energetics ci op Pressure (GPa) 59th Annual Meeting of the American Physical Society Division of Plasma Physics Milwaukee, WI October

2 Summary A solid hp4 phase of sodium has been observed at ~320 GPa Na has been previously observed to transform into an optically transparent phase at 200 GPa* The phase is predicted by simulation to be a structurally complex electride hp4 structure* Na was ramp compressed to ~320 GPa on the OMEGA EP Laser System and studied using in-situ x-ray diffraction The existence of the hp4 phase at ~320 GPa indicates that the rise of the melting temperature starting at 120 GPa continues even at higher pressures T13838 * M. Marqués et al., Phys. Rev. B 83, (2011). 2

3 ollaborators D. N. Polsin, J. R. Rygg, T. R. Boehly, L. randall, B. J. Henderson, S. X. Hu, M. Huff, R. Saha, and G. W. ollins University of Rochester Laboratory for Laser Energetics R. Smith, J. H. Eggert, and A. E. Lazicki Lawrence Livermore National Laboratory M. McMahon Department of Physics, University of Edinburgh 3

4 At high pressures, Na has a unique melting curve* that possesses a minimum at 120 GPa, then rises steeply 2000 Liquid Temperature (K) Melting curve bcc fcc mp512 o120 ti50 ap90 ti19 ci op Pressure (GPa) T13839 *M. Marqués et al., Phys. Rev. B 83, (2011), and references therein. 4

5 Diamond-anvil-cell (DA) experiments* show that Na transforms into an optically transparent phase at 200 GPa 2000 Liquid Reflecting Temperature (K) Melting curve bcc fcc mp512 o120 ti50 ap90 ti19 ci op Pressure (GPa) T13840 * Y. Ma et al., Nature 458, 182 (2009). 5

6 Diamond-anvil-cell (DA) experiments* show that Na transforms into an optically transparent phase at 200 GPa 2000 Liquid Reflecting Absorbing Temperature (K) Melting curve bcc fcc mp512 o120 ti50 ap90 ti19 ci op Pressure (GPa) T13841 * Y. Ma et al., Nature 458, 182 (2009). 6

7 Diamond-anvil-cell (DA) experiments* show that Na transforms into an optically transparent phase at 200 GPa 2000 Liquid Reflecting Absorbing Transparent Temperature (K) Melting curve bcc fcc mp512 o120 ti50 ap90 ti19 ci op Pressure (GPa) T13842 * Y. Ma et al., Nature 458, 182 (2009). 7

8 This phase is predicted* to be an electride hp4 structure, where conduction electrons are trapped in interstitial wells, producing an insulator Electron localization function a a Na1 Na2 Ion Electron A c B Na2 Na1 c a 120 b Interstitial hp4: a double-hexagonal close-packed (dhcp) structure squeezed along the c axis. T13843 * Y. Ma et al., Nature 458, 182 (2009). 8

9 The powder x-ray diffraction image-plate (PXRDIP)* diagnostic is used to obtain diffraction data of a compressed powder Na sample u He a, 1.48 Å X-ray source Image plates Laser drive VISAR** Na Tungsten pinhole collimator/reference T13844 * J. R. Rygg et al., Rev. Sci. Instrum. 83, (2012). **VISAR: velocity interferometer system for any reflector 9

10 The powder x-ray diffraction image-plate (PXRDIP)* diagnostic is used to obtain diffraction data of a compressed powder Na sample u He a, 1.48 Å X-ray source Image plates Laser drive VISAR X ray Target structure Na Tungsten pinhole collimator/reference Laser drive Na W VISAR W T13845 * J. R. Rygg et al., Rev. Sci. Instrum. 83, (2012). 10

11 The powder x-ray diffraction image-plate (PXRDIP)* diagnostic is used to obtain diffraction data of a compressed powder Na sample u He a, 1.48 Å X-ray source Image plates Delivered target drive and x-ray source drive the pulse shape Laser drive VISAR 10 0 X-ray spectrometer drive 1-ns pulse Na Tungsten pinhole collimator/reference Power (TW) 10 1 Target drive ramp pulse Time (ns) T13846 * J. R. Rygg et al., Rev. Sci. Instrum. 83, (2012). 11

12 The powder x-ray diffraction image-plate (PXRDIP)* diagnostic is used to obtain diffraction data of a compressed powder Na sample u He a, 1.48 Å X-ray source Image plates Debye Scherrer powder diffraction Laser drive VISAR 2θ 1 2θ 2 Na Tungsten pinhole collimator/reference Line x-ray source d 1 Debye Scherrer rings ompressed randomly oriented crystals T13847 * J. R. Rygg et al., Rev. Sci. Instrum. 83, (2012). 12

13 VISAR data are used to determine the velocity of the diamond free surface, which is back-propagated to determine the pressure in the Na sample Velocity (km/s) Diamond ablator 40 nm Diamond window free-surface velocity Sodium 58 nm Diamond window 77 nm VISAR Free surface VISAR raw data Pressure (GPa) Time (ns) Time (ns) T

14 Raw diffraction data are scanned from image plates on five sides of the box and projected onto a { 2i plane X-ray source Image plates 150 VISAR ( ) { i ( ) T

15 The four brightest lines are tungsten bcc* diffraction signals, which are used for calibration 150 Intensity W W W i ( ) ( ) { alibration lines T13850 * bcc: body centered cubic i ( ) 15

16 The three weaker lines are sodium diffraction lines, consistent with hp4 structure Intensity Na (011) i ( ) Na (012) Na (110) ( ) { Sodium diffraction 43.3 lines i ( ) T

17 The three weaker lines are sodium diffraction lines, consistent with hp4 structure a = 2.73 Å c = 3.72 Å c/a = 1.36 t = 6.36 g/cm 3 t/t 0 = 6.57 a a c A B Na2 a Na1 120 c b ( ) { Sodium diffraction 43.3 lines i ( ) T

18 Sodium has a solid phase at ~320 GPa, which is consistent with hp4 structure 2000 Liquid Isentrope hp4 a a Temperature (K) bcc Melting curve 200 op Pressure (GPa) fcc mp512 o120 ti50 ci16 ap90 ti19 c A B c Na2 a Na1 120 b T

19 The melting temperature rises at >120 GPa Temperature (K) Liquid bcc Liquid Isentrope Melting curve 200 op Pressure (GPa) fcc mp512 o120 ti50 ci16 ap90 ti19 hp4 c A B a a c Na2 a Na1 120 b T

20 Summary/onclusions A solid hp4 phase of sodium has been observed at ~320 GPa Na has been previously observed to transform into an optically transparent phase at 200 GPa* The phase is predicted by simulation to be a structurally complex electride hp4 structure* Na was ramp compressed to ~320 GPa on the OMEGA EP Laser System and studied using in-situ x-ray diffraction The existence of the hp4 phase at ~320 GPa indicates that the rise of the melting temperature starting at 120 GPa continues even at higher pressures T13838 * M. Marqués et al., Phys. Rev. B 83, (2011). 20