# Short-Range Wetting at Liquid Gallium-Bismuth Alloy Surfaces: X-Ray Measurements and Square-Gradient Theory

 Title: Short-Range Wetting at Liquid Gallium-Bismuth Alloy Surfaces: X-Ray Measurements and Square-Gradient Theory Author: Huber, Patrick; Shpyrko, Oleg; Pershan, Peter S.; Ocko, Ben; DiMasi, Elaine; Deutsch, Moshe Note: Order does not necessarily reflect citation order of authors. Citation: Huber, Patrick, Oleg Shpyrko, Peter S. Pershan, Ben Ocko, Elaine DiMasi, and Moshe Deutsch. 2003. Short-range wetting at liquid gallium-bismuth alloy surfaces: X-ray measurements and square-gradient theory. Physical Review B 68:085409. Full Text & Related Files: Huber_Short-Range.pdf (1.180Mb; PDF) Abstract: We present an x-ray reflectivity study of wetting at the free surface of the binary liquid metal alloy gallium-bismuth (Ga-Bi) in the region where the bulk phase separates into Bi-rich and Ga-rich liquid phases. The measurements reveal the evolution of the microscopic structure of the wetting films of the Bi-rich, low-surface-tension phase along several paths in the bulk phase diagram. The wetting of the Ga-rich bulk’s surface by a Bi-rich wetting film, the thickness of which is limited by gravity to only 50 Å, creates a Ga-rich/Bi-rich liquid/liquid interface close enough to the free surface to allow its detailed study by x rays. The structure of the interface is determined with Ångström resolution, which allows the application of a mean-field square gradient model extended by the inclusion of capillary waves as the dominant thermal fluctuations. The sole free parameter of the gradient model, the influence parameter $$\kappa$$, that characterizes the influence of concentration gradients on the interfacial excess energy, is determined from our measurements. This, in turn, allows a calculation of the liquid/liquid interfacial tension, and a separation of the intrinsic and capillary wave contributions to the interfacial structure. In spite of expected deviations from MF behavior, based on the upper critical dimensionality ($$D_u$$=3) of the bulk, we find that the capillary wave excitations only marginally affect the short-range complete wetting behavior. A critical wetting transition that is sensitive to thermal fluctuations appears to be absent in this binary liquid-metal alloy. Published Version: doi: 10.1103/PhysRevB.68.085409 Other Sources: http://www.liquids.deas.harvard.edu/peter/2003.pdf/gabiprb15.pdf Terms of Use: This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAA Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:10356591 Downloads of this work: