3,213 research outputs found
Calculation of Critical Nucleation Rates by the Persistent Embryo Method: Application to Quasi Hard Sphere Models
We study crystal nucleation of the Weeks-Chandler-Andersen (WCA) model, using
the recently introduced Persistent Embryo Method (PEM). The method provides
detailed characterization of pre-critical, critical and post-critical nuclei,
as well as nucleation rates that compare favorably with those obtained using
other methods (umbrella sampling, forward flux sampling or seeding). We further
map our results to a hard sphere model allowing to compare with other existing
predictions. Implications for experiments are also discussed.Comment: 27 pages, 11 figure
Structural and Chemical Orders in Ni64.5Zr35.5 Metallic Glass by Molecular Dynamics Simulation
The atomic structure of Ni64.5Zr35.5 metallic glass has been investigated by
molecular dynamics (MD) simulations. The calculated structure factors from the
MD glassy sample at room temperature agree well with the X-ray diffraction
(XRD) and neutron diffraction (ND) experimental data. Using the pairwise
cluster alignment and clique analysis methods, we show that there are three
types dominant short-range order (SRO) motifs around Ni atoms in the glass
sample of Ni64.5Zr35.5, i.e., Mixed-Icosahedron(ICO)-Cube, Twined-Cube and
icosahedron-like clusters. Furthermore, chemical order and medium-range order
(MRO) analysis show that the Mixed-ICO-Cube and Twined-Cube clusters exhibit
the characteristics of the crystalline B2 phase. Our simulation results suggest
that the weak glass-forming ability (GFA) of Ni64.5Zr35.5 can be attributed to
the competition between the glass forming ICO SRO and the crystalline
Mixed-ICO-Cube and Twined-Cube motifs
Effect of Samarium doping on the nucleation of fcc-Aluminum in undercooled liquids
The effect of Sm doping on the fcc-Al nucleation was investigated in Al-Sm
liquids with low Sm concentrations (xSm) with molecular dynamics simulations.
The nucleation in the moderately undercooled liquid is achieved by the recently
developed persistent-embryo method. Systematically computing the nucleation
rate with different xSm (xSm=0%, 1%, 2%, 3%, 5%) at 700 K, we found Sm dopant
reduces the nucleation rate by up to 25 orders of magnitudes with only 5%
doping concentration. This effect is mostly associated with the increase in the
free energy barrier with a minor contribution from suppression of the
attachment to the nucleus caused by Sm doping.Comment: 4 figure
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