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Title: Degenerate Ising model for atomistic simulation of crystal-melt interfaces

One of the simplest microscopic models for a thermally driven first-order phase transition is an Ising-type lattice system with nearest-neighbour interactions, an external field, and a degeneracy parameter. The underlying lattice and the interaction coupling constant control the anisotropic energy of the phase boundary, the field strength represents the bulk latent heat, and the degeneracy quantifies the difference in communal entropy between the two phases. We simulate the (stochastic) evolution of this minimal model by applying rejection-free canonical and microcanonical Monte Carlo algorithms, and we obtain caloric curves and heat capacity plots for square (2D) and face-centred cubic (3D) lattices with periodic boundary conditions. Since the model admits precise adjustment of bulk latent heat and communal entropy, neither of which affect the interface properties, we are able to tune the crystal nucleation barriers at a fixed degree of undercooling and verify a dimension-dependent scaling expected from classical nucleation theory. We also analyse the equilibrium crystal-melt coexistence in the microcanonical ensemble, where we detect negative heat capacities and find that this phenomenon is more pronounced when the interface is the dominant contributor to the total entropy. The negative branch of the heat capacity appears smooth only when the equilibrium interface-area-to-volume ratiomore » is not constant but varies smoothly with the excitation energy. Finally, we simulate microcanonical crystal nucleation and subsequent relaxation to an equilibrium Wulff shape, demonstrating the model's utility in tracking crystal-melt interfaces at the atomistic level.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4]
  1. University Chemical Laboratories, Lensfield Road, Cambridge CB2 1EW (United Kingdom)
  2. Department of Mathematics, University of Tennessee, Knoxville, Tennessee 37996-1300 (United States)
  3. The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140 (New Zealand)
  4. (New Zealand)
Publication Date:
OSTI Identifier:
22255108
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 7; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ANISOTROPY; BOUNDARY CONDITIONS; CONTROL; COUPLING CONSTANTS; CRYSTALS; ENTROPY; EXCITATION; FCC LATTICES; INTERACTIONS; INTERFACES; ISING MODEL; MONTE CARLO METHOD; NUCLEATION; PERIODICITY; PHASE TRANSFORMATIONS; SIMULATION; SPECIFIC HEAT; STOCHASTIC PROCESSES