Optimized model potentials for mercury-mercury and mercury-carbon interactions are used in molecular dynamics simulations to study wetting and solidification of liquid mercury encapsulated in single-walled carbon nanotubes. The contact angle of mercury in the nanotube cavity increases linearly with wall curvature. The solid-liquid transition becomes less well defined as nanotube diameter decreases, while the melting temperature drops exponentially. A concentric cylindrical-shell structure is predicted for solidified mercury in small ͑20,20͒ nanotubes, while a polycrystalline structure appears in larger ͑40,40͒ nanotubes. DOI: 10.1103/PhysRevB.76.195444 PACS number͑s͒: 65.80.ϩn, 02.70.Ns, 64.70.Dv Liquid mercury does not wet graphite spontaneously. Indeed, fresh mercury forms droplets on highly ordered pyrolytic graphite with a contact angle of 152.5°. 1 Being equivalent to graphene scrolls, carbon nanotubes too cannot be wetted spontaneously by mercury, or for that matter, by any liquid metal with surface tension greater than 180 mN/ m. 2 However, wetting and filling of the inner cavity of a carbon nanotube with mercury have been shown to occur as a result of electrowetting. 3 Continuous columns of liquid mercury form inside carbon nanotubes with their open end immersed into a mercury droplet, following the application of a voltage exceeding a threshold value between the nanotube and the droplet. Once confined in a nanotube cavity, the wetting behavior of a nonwetting fluid becomes of fundamental and practical interest for nanofluidics. Furthermore, studies of freezing or melting transitions of metals under onedimensional confinement could lead to the discovery of new crystalline phases and possibly to the existence of a solidliquid critical point. 4 New solid metal phases could lead to unexpected mechanical, electrical, magnetic, and catalytic properties.Ordering and crystallization of materials in carbon nanotube cavities have attracted intense theoretical interest. New ice phases, including ordered ice nanotubes, were predicted to form by freezing water inside carbon nanotubes. 5 Simulations of CCl 4 in nanotube cavities showed liquid ordering in concentric layers, which solidify into two-dimensional hexagonal crystals unlike those observed for bulk crystallization. 6 Depending on the nanotube diameter, helical-strand, cylindrical-shell, and fcc structures were predicted for Cu and Au confined inside nanotube cavities. 7,8 Experimental evidence for the existence of such new structures in nanotube cavities has been sparse. Using highresolution transmission electron microscopy, Fan et al. 9 demonstrated the formation of a double-strand helix of iodine atoms inside a ͑10,10͒ single-walled nanotube ͑SWCNT͒. In slightly larger SWCNTs, Guan et al. 10 found a new crystalline phase of iodine, in addition to a triple-strand helix. Using x-ray diffraction, Maniwa et al. 11 studied water freezing in SWCNT bundles and found a new peak appearing in the diffraction spectrum at 235 K, which was attributed to the formati...