SAP-X2C在光谱学中的应用及与屏蔽核自旋轨道近似的比较
Application of SAP-X2C to Spectroscopy and Comparison to Screened Nuclear Spin-Orbit Approximations
AI总结：
研究将用于处理单电子精确双组分（SAP-X2C）理论中双电子图像变化误差的原子势简单叠加方法推广到解析导数理论，并应用于分子光谱学，比较其与四组分结果及更简单的屏蔽核自旋轨道（SNSO）近似的准确性。
AI中文摘要：
最近，Surjuse和Valeev建议使用原子势的简单叠加来处理单电子精确双组分（SAP-X2C）理论中的双电子图像变化误差。本文将此假设推广到解析导数理论并应用于分子光谱学，评估了多种光谱的准确性，比较发现SAP-X2C和SNSO-X2C在光谱性质方面表现出色，且SAP-X2C有优势。
英文摘要：
Recently, Surjuse and Valeev [J. Chem. Theory Comput. 22, 3443-3452 (2026).] suggested to use a simple superposition of atomic potentials to account for the two-electron picture-change error in one-electron exact two-component (SAP-X2C) theory. Herein, we generalize this ansatz to analytical derivative theory and apply SAP-X2C to molecular spectroscopy. The accuracy is assessed for NMR, EPR, Mössbauer, UV/vis, as well as X-ray absorption spectroscopy. A thorough comparison with four-component results and the even simpler screened nuclear spin-orbit (SNSO) approximation reveals that both SNSO-X2C and SAP-X2C perform excellently for spectroscopic properties, with SAP-X2C yielding slightly lower errors. Another major advantage is its well defined thermodynamic limit and less empirical nature. Therefore, SAP-X2C may be expected to become the default choice to mitigate the two-electron picture-change error in density functional theory approaches for spectroscopy thanks to its accuracy, simplicity, and efficiency. More complicated approaches to account for this error based on atomic mean-field ansätze may still be relevant for high-level correlated methods and highly accurate thermochemistry.
