Surface layering

Surface layering is a quasi-crystalline structure at the surfaces of otherwise disordered liquids, where atoms or molecules of even the simplest liquid are stratified into well-defined layers parallel to the surface. While in crystalline solids such atomic layers can extend periodically throughout the entire dimension of a crystal, surface layering decays rapidly away from the surface and is limited to just a few near-surface region layers. Another difference between surface layering and crystalline structure is that atoms or molecules of surface-layered liquids are not ordered in-plane, while in crystalline solids they are.[1]

Surface layering was predicted theoretically by Stuart Rice at the University of Chicago in 1983 [2] and has been experimentally discovered by Peter Pershan (Harvard) and his group, working in collaboration with Ben Ocko (Brookhaven) and Moshe Deutsch (Bar-Ilan) in 1995 in elemental liquid mercury[3] and liquid gallium[4] using x-ray reflectivity techniques.

More recently layering has been shown to arise from electronic properties of metallic liquids, rather than thermodynamic variables such as surface tension, since surfaces of low-surface tension metallic liquids such as liquid potassium are layered,[5] while those of dielectric liquids such as water, are not.[6]

References
  1. Croxton, Clive A. (1974). Liquid State Physics–A Statistical Mechanical Introduction. Cambridge: Cambridge University Press. doi:10.1017/cbo9780511753480. ISBN 978-0-511-75348-0.
  2. D’Evelyn, Mark P.; Rice, Stuart A. (1983-04-15). "A study of the liquid–vapor interface of mercury: Computer simulation results". The Journal of Chemical Physics. AIP Publishing. 78 (8): 5081–5095. doi:10.1063/1.445376. ISSN 0021-9606.
  3. Magnussen, O. M.; Ocko, B. M.; Regan, M. J.; Penanen, K.; Pershan, P. S.; Deutsch, M. (1995-05-29). "X-Ray Reflectivity Measurements of Surface Layering in Liquid Mercury". Physical Review Letters. American Physical Society (APS). 74 (22): 4444–4447. doi:10.1103/physrevlett.74.4444. ISSN 0031-9007. PMID 10058508.
  4. Regan, M. J.; Kawamoto, E. H.; Lee, S.; Pershan, P. S.; Maskil, N.; Deutsch, M.; Magnussen, O. M.; Ocko, B. M.; Berman, L. E. (1995-09-25). "Surface Layering in Liquid Gallium: An X-Ray Reflectivity Study" (PDF). Physical Review Letters. American Physical Society (APS). 75 (13): 2498–2501. doi:10.1103/physrevlett.75.2498. ISSN 0031-9007. PMID 10059327.
  5. Shpyrko, Oleg; Huber, Patrick; Grigoriev, Alexei; Pershan, Peter; Ocko, Ben; Tostmann, Holger; Deutsch, Moshe (2003-03-14). "X-ray study of the liquid potassium surface: Structure and capillary wave excitations" (PDF). Physical Review B. American Physical Society (APS). 67 (11): 115405. doi:10.1103/physrevb.67.115405. ISSN 0163-1829. S2CID 17613642.
  6. Shpyrko, Oleg; Fukuto, Masafumi; Pershan, Peter; Ocko, Ben; Kuzmenko, Ivan; Gog, Thomas; Deutsch, Moshe (2004-06-30). "Surface layering of liquids: The role of surface tension". Physical Review B. American Physical Society (APS). 69 (24): 245423. doi:10.1103/physrevb.69.245423. ISSN 1098-0121. S2CID 53491473.
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