微量元素对Nd $_2$ Fe $_{14}$ B晶粒表面Nd离子晶场参数的影响
Effects of trace elements on the crystal field parameters of Nd ions at the surface of Nd$_2$Fe$_{14}$B grains
摘要：
使用第一性原理计算，我们调查的位置依赖性的微量元素，如O和Cu的晶场参数$A_2^0$，成比例的各向异性常数$K_u$的Nd离子放置在表面的$_2$ Fe $_{14}$ B晶粒。结果表明，当O或Cu原子位于Nd $_2$ Fe $_{14}$ B晶粒的（001）面附近时，Nd离子的$A_2^0$参数可能为负值。然而，在（110）表面，位于平衡位置的O原子提供负的$A_2^0$，而对于Cu添加物，无论Cu的位置如何，$A_2^0$都保持正。因此，当Cu原子接近Nd-Fe-B晶粒中的晶粒表面时，预期Cu原子比O原子更频繁地保持表面Nd离子的正局部$K_u$。
英文摘要：
Using first-principles calculations, we investigate the positional dependence of trace elements such as O and Cu on the crystal field parameter $A_2^0$, proportional to the anisotropy constant $K_u$ of Nd ions placed at the surface of Nd$_2$Fe$_{14}$B grains. The results suggest the possibility that the $A_2^0$ parameter of Nd ions at the (001) surface of Nd$_2$Fe$_{14}$B grains exhibits a negative value when the O or Cu atom is located near the surface, closer than its equilibrium position. At the (110) surface, however, O atoms located at the equilibrium position provide a negative $A_2^0$, while for Cu additions $A_2^0$ remains positive regardless of Cu's position. Thus, Cu atoms are expected to maintain a positive local $K_u$ of surface Nd ions more frequently than O atoms when they approach the grain surfaces in the Nd-Fe-B grains.
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