title: Experimental evidence for surface freezing in supercooled n-alkane nanodroplets.
abstract: Intermediate chain length (16 ≤i≤ 50) n-alkanes are known to surface freeze at temperatures that are up to three degrees higher than the equilibrium melting point [B. M. Ocko et al., Phys. Rev. E, 1997, 55, 3164-3182]. Our recent experimental results suggest that highly supercooled nanodroplets of n-octane and n-nonane also surface freeze, and subsequently bulk crystallization occurs. The data yield surface and bulk nucleation rates on the order of ~10(15) cm(-2) s(-1) and ~10(22) cm(-3) s(-1), respectively, at temperatures between 180 K and 200 K. Molecular dynamics simulations at the united atom level were used to follow the freezing of a supercooled n-octane drop and show that an ordered monolayer develops on the surface of the droplet almost immediately, and the rest of the droplet then freezes in a layer-by-layer manner.
authors.affiliation: William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Viraj P
authors.initials: VP
authors.lastname: Modak
authors.forename: Harshad
authors.initials: H
authors.lastname: Pathak
authors.forename: Mitchell
authors.initials: M
authors.lastname: Thayer
authors.forename: Sherwin J
authors.initials: SJ
authors.lastname: Singer
authors.forename: Barbara E
authors.initials: BE
authors.lastname: Wyslouzil
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D049329:Nanostructures / Q000737:chemistry*; D009795:Octanes / Q000737:chemistry*; D053838:Scattering, Small Angle; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D000473:Alkanes; D009795:Octanes; C017573:nonane; C026728:octane