Tew David P, Hättig Christof, Graf Nora K
Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany.
Quantum Chemistry Group, Ruhr-Universität Bochum, 44780 Bochum, Germany.
Phys Chem Chem Phys. 2019 Jul 14;21(26):14063-14072. doi: 10.1039/c8cp06952b. Epub 2019 Jan 18.
Analytic second nuclear derivatives for excited electronic state energies have been implemented for the resolution-of-the-identity accelerated CC2, CIS(D) and ADC(2) models. Our efficient implementation with O(N) memory demands enables the treatment of medium sized molecules with large basis sets and high numerical precision and thereby paves the way for semi-numerical evaluation of the higher-order derivatives required for anharmonic corrections to excited state vibrational frequencies. We compare CC2 harmonic and anharmonic excited state frequencies with experimental values for para-difluorobenzene, toluene and catechol. Basis set problems occur for out-of-plane bending vibrations due to intramolecular basis set superposition error. For non-planar molecules and in plane modes of planar molecules, the agreement between theory and experiment is better than 30 cm on average and we reassign a number of experimental bands on the basis of the ab initio predictions.
已针对恒等式加速CC2、CIS(D)和ADC(2)模型实现了激发电子态能量的解析二阶核导数。我们具有O(N)内存需求的高效实现方式能够处理具有大基组和高数值精度的中等大小分子，从而为激发态振动频率的非谐校正所需的高阶导数的半数值评估铺平了道路。我们将CC2谐波和非谐激发态频率与对二氟苯、甲苯和邻苯二酚的实验值进行了比较。由于分子内基组叠加误差，面外弯曲振动会出现基组问题。对于非平面分子和平面分子的面内模式，理论与实验之间的一致性平均优于30 cm，并且我们根据从头算预测重新指定了一些实验谱带。
