Heterogeneous Crystallization on Pairs of Pre-Structured Seeds

Abstract

Studying the effects of small pre-structured seeds on the crystallization transition in an undercooled monodisperse Lennard-Jones fluid with transition interface path sampling combined with molecular dynamics simulations, we analyze the impact of the simultaneous presence of two seeds with various structures. In the presence of seeds with face- and body-centered cubic structures, we find that decreasing the seed-to-seed distance enhances the probability of the crystalline clusters formed on one of the seeds to grow beyond the critical size, thus, increasing the crystal nucleation rates. In contrast, when seeds have an icosahedral structure, the crystalline clusters form mostly in the bulk. The crystal nucleation rate, however, is also determined by the distance between the seeds with regular structure in which the lattice spacing is equal to the bulk lattice constant, pointing to a heterogeneous crystal nucleation that occurs away from the icosahedrally structured seeds. For slightly squeezed seeds, the effects of the presence of seeds with face- and body-centered cubic structures are reduced in comparison to the regular seeds, and we do not see any effect of the presence of the second seed for seeds with squeezed icosahedral structure.

Diffusivity, Interfacial Free Energy, and Crystal Nucleation in a Supercooled Lennard-Jones Liquid

“…In favorable conditions, critical nuclei could be formed in a metastable liquid containing an embedded seed. , However, in this study, during the observation of the seed evolution in the metastable liquid (Δ t ′ = 0.5 ns), spontaneous formation of supercritical sized nuclei did not occur. In ref , at T = 0.728 T m , the homogeneous nucleation rate was J * = 1.6(1) × 10 –8 .…”

“…A significant influence in the structure of crystal seeds on the crystallization kinetics was previously detected. 17,[37][38][39][40]57 However, spherical ice seeds having different (cubic, hexagonal) structures were critical at the same temperature and had equal values of interfacial free energies, calculated via the seeding approach. 48 In this study, while preserving both the seed radius and its density, nuclei with hcp, fcc, and bcc crystal lattice were introduced.…”

“…The seeding technique was also used to unveil the crystallization of atomic and molecular model systems. For instance: Si, − colloidal fluid, , Lennard-Jones (LJ), − Cu 50 Zr 50 , , Ni, − Cr, H 2 O, ,− hard spheres, ,− Ge 2 Sb 2 Te 5 , methane hydrate, Cu, , Fe, , Au, NaCl, ,− Potts lattice model, 2D LJ, and Al . The number of particles in the embedded embryos ranged from n = 13 − to 39000, and the Gibbs number reached the upper value of W * / k B T ≈ 1100 …”

“…In most of the above listed papers ,− on the crystal seeding method, including the frequently cited ref , no comparison was made of the obtained nucleation rate, J , with its direct calculation at the same temperature for the same model system. Only in five of them ,,,, the authors extrapolated the J ( T ) calculated by the seeding method at moderate supercoolings to J data obtained by a brute-force method at high supercoolings.…”

Controlling crystallization: what liquid structure and dynamics reveal about crystal nucleation mechanisms

“…If the dynamical and structural properties of the supercooled liquid can be modified in a welldefined manner, this could provide novel technological routes towards the targeted nucleation of specific polymorphs and screening the nucleating ability of substrates. Apart from nucleating agents, such as substrates or other impurities [1,17,[61][62][63][64][65], targeted modifications of the nucleation events can be triggered experimentally by modifying the liquid structure with external stimuli such as lasers, electric fields or elongational flows. Advances in experimental techniques have made it possible to manipulate colloidal suspensions and create pattern templates using, e.g.…”