arXiv:2608.14875cond-mat.mtrl-scics.LG2026-08

机器学习泛函改进在密度泛函紧束缚中不总能继承,关键看类型是否匹配。

When do machine-learned exchange-correlation improvements inherit into density-functional tight binding?

  • 用传递比率分析发现部分泛函改进反而让带隙变差
  • 4种共价半导体中带隙变化方向相反,存在反向传递现象
  • 适合筛选可继承的元素与体系,节省参数化成本

机器学习交换关联泛函可在近半局域成本下修正带隙,而密度泛函紧束缚可处理10³–10⁶原子体系;但当前方法假设更优母体泛函带来更好参数化,我们证明这不成立。现代表泛函为轨道依赖广义Kohn-Sham算子,而参数化通道基于乘性势,无法精确表示。通过传递比率(父级变化的留存比例),我们在4种共价半导体中发现反向传递:相干负值使带隙向错误方向移动,与分子模型及r²SCAN对照一致。最小基组过隙主要由局域项约定决定,而非基组不完备;修正局域块可消除大部分过隙,再加一个d极化壳层可进一步缩小16%–40%,具体取决于空d能级位置,该位置无法由自由原子本征值唯一确定。占据流形增强、离子与闭壳排斥势可继承,而元素和III-V共价网络既不继承带隙也不继承排斥势,氧化物仅继承排斥势。我们筛查23种元素并发布参数集,表明传递比率可作为参数化前低成本预测试。

原文摘要 · Abstract (English)

Machine-learned exchange-correlation functionals correct band gaps at near-semilocal cost, while density-functional tight binding reaches the $10^3$-$10^6$-atom regime; combining them assumes that a better parent yields a better parameterization, but we show it does not. Current-generation functionals are orbital-dependent generalized Kohn-Sham operators, whereas the parameterization channel is built on a multiplicative potential, preventing exact representation. Using the transfer ratio, the surviving fraction of a parent-level change, we find anti-transfer: coherently negative ratios across four covalent semiconductors move the gap in the wrong direction, consistent with a molecular proxy and an r$^2$SCAN control. The minimal-basis overgap is dominated by the on-site convention rather than basis incompleteness; correcting the on-site block removes most of it, while one $d$-polarization shell closes a further $16$-$40%$, depending on the placement of the empty $d$ level, which no free-atom eigenvalue uniquely fixes. Occupied-manifold enhancements, ionic and closed-shell repulsive potentials, and rocksalt-oxide gaps inherit, whereas elemental and III-V covalent networks inherit neither gaps nor repulsive potentials and oxide networks inherit only the latter. We screen 23 elements and release the parameter sets, showing that the transfer ratio provides a cheap pre-test before any parameterization campaign.

泛函优化带隙预测机器学习

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