Maximum superheating and undercooling:: Systematics, molecular dynamics simulations, and dynamic experiments -: art. no. 134206

The maximum superheating and undercooling achievable at various heating (or cooling) rates were investigated based on classical nucleation theory and undercooling experiments, molecular dynamics (MD) simulations, and dynamic experiments. The highest (or lowest) temperature T-c achievable in a superheated solid (or an undercooled liquid) depends on a dimensionless nucleation barrier parameter beta and the heating (or cooling) rate Q. beta depends on the material: betaequivalent to16pigamma(sl)(3)/(3kT(m)DeltaH(m)(2)) where gamma(sl) is the solid-liquid interfacial energy, DeltaH(m) the heat of fusion, T-m the melting temperature, and k Boltzmann's constant. The systematics of maximum superheating and undercooling were established phenomenologically as beta=(A(0)-b log(10)Q)theta(c)(1-theta(c))(2) where theta(c)=T-c/T-m, A(0)=59.4, b=2.33, and Q is normalized by 1 K/s. For a number of elements and compounds, beta varies in the range 0.2-8.2, corresponding to maximum superheating theta(c) of 1.06-1.35 and 1.08-1.43 at Qsimilar to1 and 10(12) K/s, respectively. Such systematics predict that a liquid with certain beta cannot crystallize at cooling rates higher than a critical value and that the smallest theta(c) achievable is 1/3. MD simulations (Qsimilar to10(12) K/s) at ambient and high pressures were conducted on close-packed bulk metals with Sutton-Chen many-body potentials. The maximum superheating and undercooling resolved from single- and two-phase simulations are consistent with the theta(c)-beta-Q systematics for the maximum superheating and undercooling. The systematics are also in accord with previous MD melting simulations on other materials (e.g., silica, Ta and epsilon-Fe) described by different force fields such as Morse-stretch charge equilibrium and embedded-atom-method potentials. Thus, the theta(c)-beta-Q systematics are supported by simulations at the level of interatomic interactions. The heating rate is crucial to achieving significant superheating experimentally. We demonstrate that the amount of superheating achieved in dynamic experiments (Qsimilar to10(12) K/s), such as planar shock-wave loading and intense laser irradiation, agrees with the superheating systematics.