A combination of fundamental measure density functional theory and Monte Carlo computer simulation is used to determine the orientation-resolved interfacial tension and stiffness for the equilibrium hard-sphere crystal-fluid interface. Microscopic density functional theory is in quantitative agreement with simulations and predicts a tension of 0.66 kBT /σ 2 with a small anisotropy of about 0.025 kBT and stiffnesses with e.g. 0.53 kBT /σ 2 for the (001) orientation and 1.03 kBT /σ 2 for the (111) orientation. Here kBT is denoting the thermal energy and σ the hard sphere diameter. We compare our results with existing experimental findings.PACS numbers: 68.08. De, 05.20.Jj, 82.70.Dd Solidification and melting processes involve crystal-fluid interfaces that separate the disordered from the ordered phase. Understanding the properties of such interfaces on a microscopic scale is pivotal to control and optimize crystal nucleation and the emerging microstructure of the material. Important applications include the fabrication of defect-free metallic alloys [1] and of photonic [2], phononic [3] and protein [4] crystals. In equilibrium, i.e. between a coexisting crystal and fluid phase, creating a crystal-fluid interface results in a free energy penalty per area that is called interfacial tension. Unlike the liquid-gas or fluid-fluid interface, the structure of the solid-fluid interface depends on its orientation [5]. This anisotropy is associated with a difference between the interfacial tension and the interfacial stiffness of a crystalline surface.Predicting crystal-fluid interfacial tensions by a molecular theory is a very challenging task. Classical density functional theory of freezing provides a unifying framework to describe the solid and liquid on the same footing and is therefore in principle a promising tool. In this respect, the simple athermal hard sphere system which exhibits a freezing transition from a fluid into a face-centered-cubic (fcc) crystal, is an important reference system. The accuracy of previous density functional calculations of the hard sphere solid-fluid interface [6-9], however, was hampered by the lack of knowledge of a reliable functional and severe restrictions in the parametrization of the trial density profile.In this letter, interfacial tensions and stiffnesses of the equilibrium hard sphere crystal-fluid interface are predicted using fundamental measure density functional theory [10] which has been shown to predict accurate bulk freezing data [11]. The interfacial tension and stiffness for five different orientations are obtained, namely along the (001), (011), (111), (012) and (112) orientations (see Fig. 1). A small orientational anisotropy for the tensions is found and the average tension is about 0.66 k B T /σ 2 with k B T denoting the thermal energy and σ the hard sphere diameter. For the stiffnesses the data are spread in a much wider range between 0.28 k B T /σ 2 for the (011) orientation with lateral direction [100] and 1.03 k B T /σ 2 for the (111) orientation. We have als...

Crystal-liquid interfaces in nickel are investigated by molecular-dynamics computer simulations. Inhomogeneous systems of size Lx × Ly × Lz with Lz = 5Ly are prepared where the crystal fcc phase at different orientations coexists with the liquid phase, separated by planar interfaces in the xy-plane. The lateral dimensions are varied, using two different geometries with Lx = Ly and with Ly Lx. In the framework of capillary wave theory (CWT), anisotropic interfacial stiffnesses and tensions are determined using different predictions of CWT with respect to the spectrum, finite-size broadening and different geometries. From a parameterization in terms of cubic harmonics up to 8th order, the anisotropic interfacial free energy is obtained.

Nucleation in undercooled Ni is investigated by a combination of differential scanning calorimetry (DSC) experiments and Monte Carlo (MC) simulation. By systematically varying the sample size in the DSC experiments, nucleation rates J over a range of 8 orders of magnitude are obtained. Evidence is given that these rates correspond to homogeneous nucleation. Free energy barriers ΔG*, as extracted from the measured J, are in very good agreement with those from the MC simulation. The MC simulation indicates a nonspherical geometry of crystalline clusters, fluctuating between prolate and oblate shape at a given size. Nevertheless, the temperature dependence of ΔG* is well described by classical nucleation theory.

We compare experimental results from a quasi-two-dimensional colloidal hard sphere fluid to a Monte Carlo simulation of hard disks with small particle displacements. The experimental short-time self-diffusion coefficient D(S) scaled by the diffusion coefficient at infinite dilution, D(0), strongly depends on the area fraction, pointing to significant hydrodynamic interactions at short times in the experiment, which are absent in the simulation. In contrast, the area fraction dependence of the experimental long-time self-diffusion coefficient D(L)/D(0) is in quantitative agreement with D(L)/D(0) obtained from the simulation. This indicates that the reduction in the particle mobility at short times due to hydrodynamic interactions does not lead to a proportional reduction in the long-time self-diffusion coefficient. Furthermore, the quantitative agreement between experiment and simulation at long times indicates that hydrodynamic interactions effectively do not affect the dependence of D(L)/D(0) on the area fraction. In light of this, we discuss the link between structure and long-time self-diffusion in terms of a configurational excess entropy and do not find a simple exponential relation between these quantities for all fluid area fractions.