Systematic development of ab initio tight-binding models for hexagonal metals
Systematic development of ab initio tight-binding models for hexagonal metals
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DOI：
10.1103/physrevmaterials.4.043801
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发表时间：
2020-04
影响因子：
3.4
通讯作者：
J. Smutná;R. Fogarty;M. Wenman;A. Horsfield
中科院分区：
文献类型：
--
作者：
J. Smutná;R. Fogarty;M. Wenman;A. Horsfield
一种从从头算出发建立可扩展紧束缚模型的系统方法已经被开发出来，并在两种六方金属：ZR和Mg上进行了测试。讨论并量化了在每个近似级别引入的误差。对于块体材料，使用有限的SPD轨道基组足以高精度地再现fcc、bcc和hcp晶格结构的体能-体积曲线以及电子态密度。然而，双中心近似在对势项、晶场项和跳跃积分中引入了十分之几eV的误差。对前两种方法进行了与环境有关的修正，大大提高了精度。通过对一组感兴趣的结构获取多中心跳跃积分，将它们旋转到键参考系中，然后通过这些值来拟合光滑函数，从而修正了双中心跳跃积分。最后，用一对势能来修正剩余的误差。然而，这一过程不足以确保模型的可转移性，特别是在引入点缺陷的情况下。特别是，当间隙元素被添加到模型中时，它被证明是有问题的，就像八面体自间隙原子的情况所证明的那样。
A systematic method for building an extensible tight-binding model from ab initio calculations has been developed and tested on two hexagonal metals: Zr and Mg. The errors introduced at each level of approximation are discussed and quantified. For bulk materials, using a limited basis set of spd orbitals is shown to be sufficient to reproduce with high accuracy bulk energy versus volume curves for fcc, bcc, and hcp lattice structures, as well as the electronic density of states. However, the two-center approximation introduces errors of several tenths of eV in the pair potential, crystal-field terms, and hopping integrals. Environmentally dependent corrections to the former two have been implemented, significantly improving the accuracy. Two-center hopping integrals were corrected by taking many-center hopping integrals for a set of structures of interest, rotating them into the bond reference frame, and then fitting a smooth function through these values. Finally, a pair potential was fitted to correct remaining errors. However, this procedure is not sufficient to ensure transferability of the model, especially when point defects are introduced. In particular, it is shown to be problematic when interstitial elements are added to the model, as demonstrated in the case of octahedral self-interstitial atoms.