AI 中文总结
针对VASP的固定参考PAW-XCH计算中绝对跃迁能被低估的问题，通过自洽单原子计算构建全电子单原子参考修正，使修正谱接近实验能标，明确同元素化学位移由超胞总能双重差决定。
AI 中文摘要
核心损失谱的跃迁能包含可转移的原子核心参考贡献和决定化学位移的材料相关响应。密度泛函理论计算通常会低估绝对跃迁能。在VASP中，基态和核心激发占据使用相同的PAW数据集，当核心占据变化时保留基态原子参考，从而省略了相关的全电子原子参考变化。我们通过自洽单原子计算评估该变化，并从价电子参考变化和孤立原子总能响应构建残余原子参考修正。与独立的超软赝势实现的比较表明，对于K、L1和L2,3核心空穴，全电子参考具有数值一致性，而代表性的修正谱接近实验绝对能标。对于固定元素、边和核心空穴方案，原子参考项从能量差中抵消，表明同元素的化学位移由超胞总能的双重差决定。在Al和Si的L2,3边，近边谱形状还强烈依赖于低位3d类未占据态的PAW表示。
英文摘要
The transition energy of a core-loss spectrum comprises a transferable atomic core-reference contribution and a material-dependent response that determines chemical shifts. Density functional theory calculations commonly underestimate absolute transition energies. In VASP, the same PAW dataset is used for the ground and core-excited occupations, retaining the ground-state atomic reference when the core occupation changes and thereby omitting the associated all-electron atomic reference change. We evaluate this change using self-consistent single-atom calculations and construct a residual atomic reference correction from the valence reference change and isolated-atom total-energy response. Comparisons with an independent ultrasoft-pseudopotential implementation demonstrate numerical consistency of the all-electron reference for K, L1, and L2,3 core holes, while representative corrected spectra approach the experimental absolute energy scale. For a fixed element, edge, and core-hole scheme, the atomic reference terms cancel from energy differences, showing that same-element chemical shifts are governed by the double difference of the supercell total energy. At the Al and Si L2,3 edges, the near-edge spectral shape additionally depends strongly on the PAW representation of low-lying 3d-like unoccupied states.
