In this article, spherical nanoseeds of homogeneous FCC-Cu, heterogeneous yet isomorphic FCC-Ni, and heterogeneous and heteromorphic BCC-Fe are inserted into the parent Cu liquid to conduct a comparative study of homogeneous and heterogeneous nucleation, as well as subsequent growth, using the embedded seed method molecular dynamics simulations. Thermodynamic results align with Gibbs-Thomson theory, as evidenced by the linearity of T-r for homogeneous nucleation, and are qualitatively consistent with Fletcher’s theory through the nonlinearity of T-R for heterogeneous nucleation. However, the effective radius range predicted by Fletcher’s theory has been extended significantly downward. We have even identified an "anti-Fletcher region" that violates Fletcher’s criterion. A systematic analysis of nucleation rates not only clearly explains that the heterogeneous nucleation T-R lines and spontaneous nucleation at 930 K originate from the minimum nucleation rate at a given spatiotemporal scale but also reveals that the critical nucleation rate increases markedly as the heterogeneous seed radius decreases within the anti-Fletcher region—an as-yet-unexplained phenomenon. The isomorphic FCC-Cu and FCC-Ni systems exhibit nearly identical growth patterns, in which the nested tetrahedral lamellar (NTL) structure is favored. In contrast, heterogeneous and heteromorphic BCC-Fe seeds strongly enhance lamellar (LAM) growth, weaken NTL formation, and completely suppress fivefold twinning (FFT). Observations of independent free grain growth indicate the following order of microscopic growth rates: <InlineEquation ID="IEq1"> <EquationSource Format="TEX">${\varpi }_{\text{Cu}} > {\varpi }_{\text{Ni}} > {\varpi }_{\text{Fe}}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>ϖ</mi> <mtext>Cu</mtext> </msub> <mo>></mo> <msub> <mi>ϖ</mi> <mtext>Ni</mtext> </msub> <mo>></mo> <msub> <mi>ϖ</mi> <mtext>Fe</mtext> </msub> </mrow> </math></EquationSource> </InlineEquation> for both LAM and NTL patterns, whereas the inverse trend <InlineEquation ID="IEq2"> <EquationSource Format="TEX">${\varpi }_{\text{Ni}} > {\varpi }_{\text{Cu}}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>ϖ</mi> <mtext>Ni</mtext> </msub> <mo>></mo> <msub> <mi>ϖ</mi> <mtext>Cu</mtext> </msub> </mrow> </math></EquationSource> </InlineEquation> holds for the FFT pattern. Finally, the greater the crystalline mismatch between the seed and parent Cu, the lower the fraction of HCP stacking faults in the final structure.

Molecular Dynamics Simulation of Homogeneous Cu and Heterogeneous Fe/Ni Seed-Induced Solidification in Liquid Cu via Embedded Seed Method

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发表日期：

2025年12月16日

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Tao Zhou,
YongQuan Wu

摘要

In this article, spherical nanoseeds of homogeneous FCC-Cu, heterogeneous yet isomorphic FCC-Ni, and heterogeneous and heteromorphic BCC-Fe are inserted into the parent Cu liquid to conduct a comparative study of homogeneous and heterogeneous nucleation, as well as subsequent growth, using the embedded seed method molecular dynamics simulations. Thermodynamic results align with Gibbs-Thomson theory, as evidenced by the linearity of T*-r* for homogeneous nucleation, and are qualitatively consistent with Fletcher’s theory through the nonlinearity of T*-R* for heterogeneous nucleation. However, the effective radius range predicted by Fletcher’s theory has been extended significantly downward. We have even identified an "anti-Fletcher region" that violates Fletcher’s criterion. A systematic analysis of nucleation rates not only clearly explains that the heterogeneous nucleation T*-R* lines and spontaneous nucleation at 930 K originate from the minimum nucleation rate at a given spatiotemporal scale but also reveals that the critical nucleation rate increases markedly as the heterogeneous seed radius decreases within the anti-Fletcher region—an as-yet-unexplained phenomenon. The isomorphic FCC-Cu and FCC-Ni systems exhibit nearly identical growth patterns, in which the nested tetrahedral lamellar (NTL) structure is favored. In contrast, heterogeneous and heteromorphic BCC-Fe seeds strongly enhance lamellar (LAM) growth, weaken NTL formation, and completely suppress fivefold twinning (FFT). Observations of independent free grain growth indicate the following order of microscopic growth rates: ${\varpi }_{\text{Cu}} > {\varpi }_{\text{Ni}} > {\varpi }_{\text{Fe}}$ $ϖ_{Cu} > ϖ_{Ni} > ϖ_{Fe}$ for both LAM and NTL patterns, whereas the inverse trend ${\varpi }_{\text{Ni}} > {\varpi }_{\text{Cu}}$ $ϖ_{Ni} > ϖ_{Cu}$ holds for the FFT pattern. Finally, the greater the crystalline mismatch between the seed and parent Cu, the lower the fraction of HCP stacking faults in the final structure.