弥散强化面向等离子体元件的机器学习原子间相互作用势
Machine Learned Interatomic Potential for Dispersion Strengthened Plasma Facing Components
摘要：
钨（W）是偏滤器材料的选择材料，这是由于其高熔化温度、热导率和溅射阈值。然而，W具有非常高的脆韧转变温度，并且在聚变反应堆温度（$\geq$ 1000 K）下可经历再结晶和晶粒生长。碳化锆（ZrC）弥散强化W可以改善塑性并限制晶粒长大，但弥散体对高温下组织演变和热机械性能的影响尚不清楚。我们提出了一个机器学习的光谱邻居分析潜力（SNAP）的W-ZrC，现在可以用来研究这些材料。为了构建一个潜在的适合于大规模的原子模拟在聚变反应堆的温度，它是必要的训练从头计算数据产生的一组不同的结构，化学环境和温度。进一步的精度和稳定性测试的潜力，实现了使用目标函数的材料性能和高温稳定性。晶格参数，表面能，体积模量，和热膨胀的验证确认优化的潜力。对W/ZrC双晶的拉伸试验表明，W（110）-ZrC（111）C端双晶在室温下具有最高的抗拉强度，但强度随温度的升高而降低。在2500 K时，终止层C扩散到W中，导致W-Zr界面变弱。同时，W（110）-ZrC（111）Zr封端的双晶在2500 K具有最高的抗拉强度。
英文摘要：
Tungsten (W) is a material of choice for the divertor material due to its high melting temperature, thermal conductivity, and sputtering threshold. However, W has a very high brittle-to-ductile transition temperature and at fusion reactor temperatures ($\geq$1000K) may undergo recrystallization and grain growth. Dispersion-strengthening W with zirconium carbide (ZrC) can improve ductility and limit grain growth, but much of the effects of the dispersoids on microstructural evolution and thermomechanical properties at high temperature are still unknown. We present a machine learned Spectral Neighbor Analysis Potential (SNAP) for W-ZrC that can now be used to study these materials. In order to construct a potential suitable for large-scale atomistic simulations at fusion reactor temperatures, it is necessary to train on ab initio data generated for a diverse set of structures, chemical environments, and temperatures. Further accuracy and stability tests of the potential were achieved using objective functions for both material properties and high temperature stability. Validation of lattice parameters, surface energies, bulk moduli, and thermal expansion is confirmed on the optimized potential. Tensile tests of W/ZrC bicrystals show that while the W(110)-ZrC(111) C-terminated bicrystal has the highest ultimate tensile strength (UTS) at room temperature, observed strength decreases with increasing temperature. At 2500K, the terminating C layer diffuses into the W, resulting in a weaker W-Zr interface. Meanwhile, the W(110)-ZrC(111) Zr-terminated bicrystal has the highest UTS at 2500K.
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