Crystal Growth in the Presence of Surface Melting: Novel Behavior of the Principal Facets of Ice

We present measurements of the growth rates of the principal facet surfaces of ice from water vapor as a function of supersaturation over the temperature range −2 ≥ T ≥ −40 C. Our data are well described by a dislocation-free layer-nucleationmodel, parameterized by the attachment coefficient as a function of supersaturation α(σ) = A exp(−σ0/σ). The measured parameters A(T ) and σ0(T ) for the basal and prism facets exhibit a complex behavior that likely originates from structural changes in the ice surface with temperature, in particular the onset and development of surface melting for T > −15 C. From σ0(T ) we extract the terrace step energy β(T ) as a function of temperature for both facet surfaces. As a basic property of the equilibrium ice surface, the step energy β(T ) may be amenable to calculation using molecular dynamics simulations, potentially yielding new insights into the enigmatic surface structure of ice near the triple point.