论文标题
通过平方梯度最小化和混合构型的重新耦合，在密度功能理论上对自由基的核心水平光谱的准确预测
Accurate prediction of core-level spectra of radicals at density functional theory cost via square gradient minimization and recoupling of mixed configurations
论文作者
论文摘要
与传统的线性响应协议相比，州特异性轨道优化方法在预测核心水平光谱方面更为准确，但是由于其“变异崩溃”的风险降低到基础状态，它们的效用受到限制。我们采用了最近开发的方梯度最小化（SGM，J。Chem。理论计算。16，1699-1710，2020）算法可靠地避免避免变异性崩溃，并研究轨道优化密度功能理论（DFT）在预测第二个周期元素1S核心1S核心系统的有效性。发现几个密度函数（包括扫描，B3LYP和$ω$ b97x-d3）可以预测从可用的实验数据，可预测从核心到单一占用水平的激发能量到高精度（$ \ le 0.3 $ ev rms误差）。然而，由于本质上具有多种配置，更高的激发状态更具挑战性。因此，我们提出了一条启发的途径，以自愿回收从DFT获得的单个决定符混合构型，以获得近似的双重态。该重新耦合方案用于预测Allyl激进的C K-EDGE光谱，Co $^+$的O K边缘光谱以及NO $ _2 $的N K-EDGE相对于实验的高精度，这表明使用这种核心级别的核心光谱进行了多个dumpereent conformations conforment conforment conforment conforment conforment conforment conforment conforment conforment conforment epentent epentent dft dft dft dft dft dft dft，unim-em-ccypl unim-unif unim-unim-unif unim-unim-cccd）。我们还介绍了从轨道优化的DFT计算核心兴奋状态的一般指南。
State-specific orbital optimized approaches are more accurate at predicting core-level spectra than traditional linear-response protocols, but their utility had been restricted on account of the risk of `variational collapse' down to the ground state. We employ the recently developed square gradient minimization (SGM, J. Chem. Theory Comput. 16, 1699-1710, 2020) algorithm to reliably avoid variational collapse and study the effectiveness of orbital optimized density functional theory (DFT) at predicting second period element 1s core-level spectra of open-shell systems. Several density functionals (including SCAN, B3LYP and $ω$B97X-D3) are found to predict excitation energies from the core to singly occupied levels to high accuracy ($\le 0.3$ eV RMS error), against available experimental data. Higher excited states are however more challenging by virtue of being intrinsically multiconfigurational. We thus present a CI inspired route to self-consistently recouple single determinant mixed configurations obtained from DFT, in order to obtain approximate doublet states. This recoupling scheme is used to predict the C K-edge spectra of the allyl radical, the O K-edge spectra of CO$^+$ and the N K-edge of NO$_2$ to high accuracy relative to experiment, indicating substantial promise in using this approach for computation of core-level spectra for doublet species (vs more traditional time dependent DFT, EOM-CCSD or using unrecoupled mixed configurations). We also present general guidelines for computing core-excited states from orbital optimized DFT.
