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arXiv 2003.11162cond-mat.str-elcond-mat.mtrl-sci
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自旋相关跳跃的从头算紧束缚模型的局域力方法

Local force method for the ab initio tight-binding model with spin-dependent hopping

Takuya Nomoto, Takashi Koretsune, Ryotaro Arita

摘要:

为了从第一性原理出发估算金属磁体的居里温度,我们发展了一种适用于自旋密度泛函理论中自旋相关跳跃的紧束缚模型的局域力方法.虽然自旋相关的跳跃是至关重要的自洽映射到有效的自旋模型,在传统的格林函数方案处理这样的非本地条款的数值成本是非常昂贵的。在这里,我们提出了一种基于核多项式方法(KPM),这使得计算效率显着的形式主义。我们进行了基准计算的bcc-Fe,fcc-Co,和fcc-Ni,并发现磁非本地条款的影响是特别突出的bcc-Fe。我们还提出了几个局部近似的磁非局部项,我们可以应用格林函数的方法,并通过利用格林函数的中间表示进一步降低数值成本。通过比较KPM和局部方法的结果,我们讨论了哪种局部方法最成功。我们的方法提供了一种有效的方法来估计具有复杂自旋组态的金属磁体的居里温度。

英文摘要:

To estimate the Curie temperature of metallic magnets from first principles, we develop a local force method for the tight-binding model having spin-dependent hopping derived from spin density functional theory. While spin-dependent hopping is crucial for the self-consistent mapping to the effective spin model, the numerical cost to treat such non-local terms in the conventional Green's function scheme is formidably expensive. Here, we propose a formalism based on the kernel polynomial method (KPM), which makes the calculation dramatically efficient. We perform a benchmark calculation for bcc-Fe, fcc-Co, and fcc-Ni and find that the effect of the magnetic non-local terms is particularly prominent for bcc-Fe. We also present several local approximations to the magnetic non-local terms for which we can apply the Green's function method and reduce the numerical cost further by exploiting the intermediate representation of the Green's function. By comparing the results of the KPM and local methods, we discuss which local method works most successfully. Our approach provides an efficient way to estimate the Curie temperature of metallic magnets with a complex spin configuration.

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