Скачать презентацию The Surface Structure of Liquid Metals and Alloys Скачать презентацию The Surface Structure of Liquid Metals and Alloys

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The Surface Structure of Liquid Metals and Alloys * Current associates are underlined Non-Harvard The Surface Structure of Liquid Metals and Alloys * Current associates are underlined Non-Harvard Collaborators: Ben Ocko, Elaine Di. Masi, 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. Support: DE-FG 02 -88 -ER 45379/NSF- DMR-0124936

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

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

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

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

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

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

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

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

Issue 1 What other metals can be studied? h (i. e. T/g) must be 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) Element Ga Hg Sn In K Zn Al Cu Cd Bi Li (Chemistry) Au Tl Pb Tm (K) 302. 93 234. 28 505. 118 429. 32 336. 8 692. 73 933. 52 1356. 6 594. 1 544. 5 453. 69 1337. 58 576. 7 600. 64 718 498 560 556 388 782 914 1303 570 378 398 1169 464 458 Tm/ 0. 42 0. 47 0. 90 0. 77 0. 89 1. 02 1. 04 1. 44 1. 14 1. 24 1. 31 P_melt(mm) 1. 2 E-06 ~1. 0 E-6 2. 2 E-01 9. 7 E-04 1. 1 E-01 1. 6 E-05

Measurement of Potassium h Debye-Waller X 10 -2 Good: Oxides Dissolve in Bulk Liquid Measurement of Potassium h Debye-Waller X 10 -2 Good: Oxides Dissolve in Bulk Liquid Clean Surface Bad: Low g h at layering peak is large, R(Qz) too small Ga In K Maximum Qz~0. 85 QPeak Data Layering in K is same as Ga, In.

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

Is there experimental evidence that dielectric liquids are not layered? Water: g=73 dynes/cm K: Is there experimental evidence that dielectric liquids are not layered? Water: g=73 dynes/cm K: g 100 dynes/cm R(Qz)/RF(Qz) R(Qz) Ga K H 2 O Water does not show indication of surface layering!

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

Keep Looking: i. e. Alloys for Electronics Example: Au. Si Low Temperature Eutectic Au. Keep Looking: i. e. Alloys for Electronics Example: Au. Si Low Temperature Eutectic Au. Si Diffuse Scattering Alloy is Liquid =780 dynes/cm

Summary 1 - To Measure Liquid Surface Structure Factor |F(Qz)| Effects of Capillary Waves. 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 Ga. Bi: Short Range Wetting Au. Si: Enormously Intense Future