论文标题
核心分离的相似性转化了用于核心激发光谱的EOM-CCSD方法
A Core-Valence Separated Similarity Transformed EOM-CCSD Method for Core-excitation Spectra
论文作者
论文摘要
我们介绍了K-Edge核心激发光谱的核心价相似性转化的EOM-CCSD（Steom-CCSD）方法的理论和实施。该方法可以使用顺式天然轨道和靠近黑匣子选择合适的活动空间。在单个激发的空间中，第二种相似性转化汉密尔顿被对角线化。因此，由于核心激发态的连续体耦合，最终的对角步骤摆脱了融合问题。在Steom-CCSD中的核心离子状态计算可能会出现收敛故障。已经实施了与基于天然轨道的活动空间选择兼容的核心价分离方案（CVS）以克服问题。 CVS-STEOM-CCSD具有与标准CVS-EOM-CCSD方法相似的精度，但计算成本较低。突出显示了由于使用CIS天然轨道所需的修改。通过模拟甘氨酸和胸腺素的K边缘光谱，证明了CVS-Steom-CCSD对化学应用的适用性。
We present the theory and implementation of a core-valence separated similarity transformed EOM-CCSD (STEOM-CCSD) method for K-edge core excitation spectra. The method can select an appropriate active space using CIS natural orbitals and near black box to use. The second similarity transformation Hamiltonian is diagonalized in the space of single excitation. Therefore, the final diagonalization step is free from the convergence problem arising because of the coupling of the core-excited states with the continuum of doubly excited states. Convergence trouble can appear for the preceding core-ionized states calculation in STEOM-CCSD. A core-valence separation scheme (CVS) compatible with the natural orbital based active space selection has been implemented to overcome the problem. The CVS-STEOM-CCSD has similar accuracy as that of the standard CVS-EOM-CCSD method but comes with a lower computational cost. The modification required for the CVS scheme because of the use of CIS natural orbital is highlighted. The suitability of CVS-STEOM-CCSD for chemical application is demonstrated by simulating the K-edge spectra of glycine and thymine.
