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The Surface Structure of Liquid Metals and Alloys

The Surface Structure of Liquid Metals and Alloys. * Current associates are underlined. Non-Harvard Collaborators: Ben Ocko , Elaine DiMasi, Olaf Magnussen Physics Dept. Brookhaven National Laboratory Moshe Deutsch : Bar Ilan University, Israel

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The Surface Structure of Liquid Metals and Alloys

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  1. The Surface Structure of Liquid Metals and Alloys * Current associates are underlined Non-Harvard Collaborators: Ben Ocko, Elaine DiMasi, Olaf Magnussen Physics Dept. Brookhaven National Laboratory Moshe Deutsch:Bar Ilan University, Israel Binhua Lin, Mati Meron, Tim Graber, Jeff Gerbhardt, Advanced Photon Source Harvard Students/Postdocs Alexei Grigoriev,Patrick Huber, E.H. Kawamoto, Holger Tostmann, Mike Regan,Oleg Shpyrko. Oleg Shpyrko Support: DE-FG02-88-ER45379/NSF- DMR-0124936

  2. Metallic Liquids Dielectric Liquids Vapor: Neutral Atoms Interactions are Same in Vapor and Liquid Different Interactions Liquid: Positive Ions in Sea of Negative Fermi Liquid Liquid Surfaces: Metals/Non-Metals Are Different D'Evelyn & . Rice, J. Chem. Phys., 1983. 78: p. 5225. For Metals Particle-Particle InteractionsChange Across The Surface This influences the structure of the surface!

  3. Metallic Liquids: Layers @Free Surface Chapela & Saville, 1978 D'Evelyn & Rice, 1983 Hard Wall = > Layers Free Surface No-Layer Predictions of Monte Carlo Calculations Average Density <r(z)> vs Distance From Surface(z) Non-Metal Liquids Liquid/Vapor Surface Structure Factor F(Qz)

  4. Qz Surface Normal Wave vector Transfer Measured Hg (1995) Ga (1996) In (1999) Surface Structure Factor Hg R(Qz)~|F(Qz)|2 Prediction: Constructive Interference Qz=(4p/l)sin a =(2p/D) Ga In Note Difference X-ray Reflectivity: R(Qz) & F(Qz) Quantitative Measure of F(Qz)!

  5. Ideal Flat Surface: Fresnel RF(Qz) Structure Factor F(Qz) Thermal Factor R(Qz) = Thermal Roughness Phase Shifts Differential Cross Section: Parallel Surface Wave Vector Transfer Qx Thermal Effects on Reflectivity

  6. Liquid Solid Liquid Surface •2D SurfaceTension •Gravity(|x-x’|~mm) Resolution Independent of Resolution Depends on Resolution Liquid vs Solid Surfaces

  7. Ideal Flat Surface: Fresnel RF(Qz) R(Qz) Structure Factor F(Qz) Thermal Factor Q(Qz,T) R(Qz) = g : Surface Tension Measure of Structure Factor Requires Thermal Effects be Removed Large (T/g)Qz2 ••• No specular peak if h~2!•••

  8. Diffuse Scattering for Liquid Indium Solid Lines: Theory Known Surface Tension g is OnlyAdjustable Parameter To Understand Thermal EffectsDiffuse Scattering From Liquid Surface Qx=(2p/l)[cos a-cos b] Qz=(2p/l)[sin a+sin b]

  9. Electron Density Profile Average Electron Density Indium (with/without T effects). Electron Density: Ga and In Demonstration of Thermal Removed:Liquid Gallium

  10. Issue 1 What other metals can be studied? h (i.e. T/g) must be small P & T : low enough for UHV(Hg, K, Na are special) ElementTm (K)Tm/gP_melt(mm) Ga302.937180.42 Hg234.284980.471.2E-06 Sn505.1185600.90 In429.325560.77 K336.83880.87~1.0E-6 Zn692.737820.892.2E-01 Al933.529141.02 Cu1356.613031.049.7E-04 Cd594.15701.041.1E-01 Bi544.53781.44 Li (Chemistry)453.693981.14 Au1337.5811691.141.6E-05 Tl576.74641.24 Pb600.644581.31

  11. Ga In Debye-Waller X 10-2 K h Maximum Qz~0.85QPeak Measurement of Potassium Good: Oxides Dissolve in Bulk LiquidClean Surface Bad: Low g  h at layering peak is large, R(Qz) too small Data  Layering in K is same as Ga, In.

  12. Bump Not seen in Ga,In R(Qz) Possible Model Spacing of 1st Layer Reduced~10% Anomalous Layering of Liquid Sn Surface Bump  Surface Density Is Higher Than Bulk!

  13. R(Qz)/RF(Qz) R(Qz) Ga K H2O Is there experimental evidence that dielectric liquids are not layered? Water: g=73 dynes/cm K: g100 dynes/cm Water does not show indication of surface layering!

  14. GaBi: Binary Phase Diagram Thickness of heavier Bi rich layer. Bi Ga If we can’t study other pure metals, what can we do? •Alloys•Surface Chemistry of Liquid Metals (oxidation) Surface: Heavier Bi rich liquid Bulk: lighter Ga rich liquid! Short Range Wetting

  15. Low Temperature Eutectic AuSi Diffuse ScatteringAlloy is Liquid g=780 dynes/cm Keep Looking: i.e. Alloys for ElectronicsExample: AuSi

  16. Summary 1- To Measure Liquid Surface Structure Factor |F(Qz)|Effects of Capillary Waves. 2- |F(Qz)| of Free Surface of Liquid Metals Exhibits Atomic Layering! 3- Water does Not! What about other non-metallic liquids. 4- Surfaces of Liquid Alloys: Interesting Physics Sn: Anomalous Surface GaBi: Short Range Wetting AuSi: Enormously Intense Future

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