Molecular dynamics simulations of solid state recrystallization I: Observation of grain growth in annealed iron nanoparticles
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109 (United States)
Molecular dynamics simulations of solid state recrystallization and grain growth in iron nanoparticles containing 1436 atoms were carried out. During the period of relaxation of supercooled liquid drops and during thermal annealing of the solids they froze to, changes in disorder were followed by monitoring changes in energy and the migration of grain boundaries. All 27 polycrystalline nanoparticles, which were generated with different grain boundaries, were observed to recystallize into single crystals during annealing. Larger grains consumed the smaller ones. In particular, two sets of solid particles, designated as A and B, each with two grains, were treated to generate 18 members of each set with different thermal histories. This provided small ensembles (of 18 members each) from which rates at which the larger grain engulfed the smaller one, could be determined. The rate was higher, the smaller the degree of misorientation between the grains, a result contrary to the general rule based on published experiments, but the reason was clear. Crystal A, which happened to have a somewhat lower angle of misorientation, also had a higher population of defects, as confirmed by its higher energy. Accordingly, its driving force to recrystallize was greater. Although the mechanism of recrystallization is commonly called nucleation, our results, which probe the system on an atomic scale, were not able to identify nuclei unequivocally. By contrast, our technique can and does reveal nuclei in the freezing of liquids and in transformations from one solid phase to another. An alternative rationale for a nucleation-like process in our results is proposed. - Graphical Abstract: Time dependence of energy per atom in the quenching of liquid nanoparticles A-C of iron. Nanoparticle C freezes directly into a single crystal but A and B freeze to solids with two grains. A and B eventually recrystallize into single crystals. Highlights: Black-Right-Pointing-Pointer Solid state material synthesis. Black-Right-Pointing-Pointer Experimental study of nucleation in condensed materials. Black-Right-Pointing-Pointer Computation Study of nucleation in condensed materials. Black-Right-Pointing-Pointer Observation of recrystallization in atomic detail.
- OSTI ID:
- 21612878
- Journal Information:
- Journal of Solid State Chemistry, Vol. 185; Other Information: DOI: 10.1016/j.jssc.2011.09.015; PII: S0022-4596(11)00506-8; Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ANNEALING
DEFECTS
GRAIN BOUNDARIES
GRAIN GROWTH
IRON
LIQUIDS
MIGRATION
MOLECULAR DYNAMICS METHOD
MONITORING
MONOCRYSTALS
NANOSTRUCTURES
NUCLEATION
PARTICLES
POLYCRYSTALS
RECRYSTALLIZATION
RELAXATION
SIMULATION
SOLIDS
SYNTHESIS
TIME DEPENDENCE
CALCULATION METHODS
CRYSTALS
ELEMENTS
FLUIDS
HEAT TREATMENTS
METALS
MICROSTRUCTURE
TRANSITION ELEMENTS