title: Heterogeneity in homogeneous nucleation from billion-atom molecular dynamics simulation of solidification of pure metal.
abstract: Can completely homogeneous nucleation occur? Large scale molecular dynamics simulations performed on a graphics-processing-unit rich supercomputer can shed light on this long-standing issue. Here, a billion-atom molecular dynamics simulation of homogeneous nucleation from an undercooled iron melt reveals that some satellite-like small grains surrounding previously formed large grains exist in the middle of the nucleation process, which are not distributed uniformly. At the same time, grains with a twin boundary are formed by heterogeneous nucleation from the surface of the previously formed grains. The local heterogeneity in the distribution of grains is caused by the local accumulation of the icosahedral structure in the undercooled melt near the previously formed grains. This insight is mainly attributable to the multi-graphics processing unit parallel computation combined with the rapid progress in high-performance computational environments.Nucleation is a fundamental physical process, however it is a long-standing issue whether completely homogeneous nucleation can occur. Here the authors reveal, via a billion-atom molecular dynamics simulation, that local heterogeneity exists during homogeneous nucleation in an undercooled iron melt.
authors.affiliation: Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan. shibuta@material.t.u-tokyo.ac.jp.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Shibuta
authors.affiliation: Graduate School of Science and Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Sakane
authors.affiliation: Graduate School of Science and Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan.
authors.forename: Eisuke
authors.initials: E
authors.lastname: Miyoshi
authors.affiliation: Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Okita
authors.affiliation: Faculty of Mechanical Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Takaki
authors.affiliation: Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan.
authors.forename: Munekazu
authors.initials: M
authors.lastname: Ohno
mesh_terms: D016880:Anisotropy; D003080:Cold Temperature; D003196:Computer Graphics; D003460:Crystallization; D005615:Freezing; D007501:Iron / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D044367:Phase Transition; D013816:Thermodynamics
chemical_list: D007501:Iron