Surface layering explained

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]

Notes and References

1. Book: Croxton, Clive A. . Liquid State Physics–A Statistical Mechanical Introduction . Cambridge University Press . Cambridge . 1974 . 978-0-511-75348-0 . 10.1017/cbo9780511753480 .
2. D’Evelyn . Mark P. . Rice . Stuart A. . A study of the liquid–vapor interface of mercury: Computer simulation results . The Journal of Chemical Physics . AIP Publishing . 78 . 8 . 1983-04-15 . 0021-9606 . 10.1063/1.445376 . 5081–5095.
3. Magnussen . O. M. . Ocko . B. M. . Regan . M. J. . Penanen . K. . Pershan . P. S. . Deutsch . M. . X-Ray Reflectivity Measurements of Surface Layering in Liquid Mercury . Physical Review Letters . American Physical Society (APS) . 74 . 22 . 1995-05-29 . 0031-9007 . 10.1103/physrevlett.74.4444 . 4444–4447. 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. . Surface Layering in Liquid Gallium: An X-Ray Reflectivity Study . Physical Review Letters . American Physical Society (APS) . 75 . 13 . 1995-09-25 . 0031-9007 . 10.1103/physrevlett.75.2498 . 2498–2501. 10059327 .
5. Shpyrko . Oleg . Huber . Patrick . Grigoriev . Alexei . Pershan . Peter . Ocko . Ben . Tostmann . Holger . Deutsch . Moshe . X-ray study of the liquid potassium surface: Structure and capillary wave excitations . Physical Review B . American Physical Society (APS) . 67 . 11 . 2003-03-14 . 0163-1829 . 10.1103/physrevb.67.115405. cond-mat/0406585 . 115405. 17613642 .
6. Shpyrko . Oleg . Fukuto . Masafumi . Pershan . Peter . Ocko . Ben . Kuzmenko . Ivan . Gog . Thomas . Deutsch . Moshe . Surface layering of liquids: The role of surface tension . Physical Review B . American Physical Society (APS) . 69 . 24 . 2004-06-30 . 1098-0121 . 10.1103/physrevb.69.245423. cond-mat/0406579 . 245423. 53491473 .