Synchrotron Studies of Liquid Metal Surfaces

• Applicant: Dr. Stefan Mechler
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2008 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 76429068

The goal of the research proposal was to develop basic understanding of the atomic structure of the surfaces of liquid metals and alloys by means of synchrotron radiation. The combination of x-ray reflectivity, off-specular diffuse scattering and grazing incidence diffraction allows for a complete description of the atomic structure in the plane of the surface and normal to the surface. Special focus was laid on the physical origin of the existence of 2D crystalline phases at the surface of liquid eutectic Au82Si18 that was discovered earlier and for which yet no theoretical explanation exists.One idea that we had considered is that crystalline surface phases arise from the large negative heat of mixing between Au and Si that leads to a high degree of chemical and topological short range order already in the bulk liquid Au82Si18. For all metallic liquids investigated so far the surface induces atomic layering parallel to the surface and the thought is that for Au82Si18 this might lead to in-plane 2D long-range crystalline order. Consequently other systems like Pd-Si, Pd-Ge that show comparable mixing enthalpies and phase diagrams like Au-Si were so far investigated within the lifetime of the fellowship. Furthermore, the study of liquid metal surfaces was extended to new classes of material like pure Ge that has a distinctly different bulk liquid structure than metallic liquids and to multicomponent bulk metallic glass forming liquids.Because of the availability of new instrumentation at the beamline Chem- MatCARS at APS the surface structure of liquid Au82Si18 measurements of details of the surface of structure of liquid Au82Si18 that could not previously be studied allowed a much more coherent and physically realistic understandinig of the surface phases.1

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Dr. Peter Pershan