Calculation of anharmonic IR and Raman intensities for periodic systems from DFT Calculations. Implementation and Validation.
Calculation of anharmonic IR and Raman intensities for periodic systems from DFT Calculations. Implementation and Validation.
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通过 DFT 计算计算周期系统的非谐波 IR 和拉曼强度。
DOI：
10.1021/acs.jctc.9b01061
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发表时间：
2020
影响因子：
5.5
通讯作者：
Michel Rérat
中科院分区：
文献类型：
--
作者：
P. Carbonnière;A. Erba;Falk F Richter;R. Dovesi;Michel Rérat
CRYSTAL程序的扩展允许计算周期性系统的非谐红外（IR）强度和拉曼活性。这项工作是一个后续的两篇论文，致力于从DFT计算固体的非谐振动态的计算，第一部分：描述的势能面（J.化学理论计算。15（2019）3755-3765）和第II部分：VSCF和VCI方法的实施（J. Chem. Theory Comput. 15（2019）3766-3777）。这里提出的方法依赖于评估的偶极矩和极化率运营商的积分从VSCF或VCI计算获得的非谐波波函数。有了这个扩展，该程序现在可以更完整地描述密度泛函理论中固体的振动光谱特征。特别地，它能够（i）为最强的光谱特征提供可靠的位置和强度，以及（ii）检查第一泛音或组合带是否具有非零IR强度或拉曼活性。因此，可以将对应于基本跃迁周围的卫星峰的跃迁，或通过最强模-模耦合与其相应的基本跃迁一样强的泛音或组合带，如所谓的费米共振。本方法是评估两个分子系统，H2O和H2 CO，以及两个固态的情况下，硼氢化BH 4和它们的氘代物种BD 4在碱金属（M=Na，K）的结晶环境。固态的情况是特别有见地的，因为在这里考虑的B-H（或B-D）伸缩区域中，它们表现出许多完全由于非谐效应的光谱特征：在IR光谱中三分之二，在拉曼光谱中六分之四。所有的红外和拉曼活性泛音和实验观察到的组合带与我们的方法是正确的预测。所采用的量子化学模型（DFT交换相关功能/基组）的电子结构计算上的计算光谱的影响进行了讨论，发现是显着的，这表明一些特殊的照顾是需要分析的微妙的光谱特征。
An extension of the CRYSTAL program is presented allowing for calculations of anharmonic Infrared (IR) intensities and Raman activities for periodic systems. This work is a follow up of two papers devoted to the computation of anharmonic vibrational states of solids from DFT calculations, part I: description of the potential energy surface (J. Chem. Theory Comput. 15 (2019) 3755-3765) and part II: implementation of the VSCF and VCI methods (J. Chem. Theory Comput. 15 (2019) 3766-3777). The approach presented here relies on the evaluation of integrals of the dipole moment and polarizability operators over anharmonic wavefunctions obtained from either VSCF or VCI calculations. With this extension, the program now allows for a more complete characterization of the vibrational spectroscopic features of solids within the density functional theory. In particular, it is able (i) to provide reliable positions and inten-sities for most intense spectral features, and (ii) to check whether a first overtone or a combi-nation band has a non-vanishing IR intensity or Raman activity. Therefore, it becomes possi-ble to assign the transition(s) corresponding to satellite peak(s) around a fundamental transi-tion, or the overtones or combination bands that may be as intense as their corresponding fun-damental transitions through the strongest mode-mode couplings, as in so-called Fermi reso-nances. The present method is assessed on two molecular systems, H2O and H2CO, as well as on two solid state cases, Boron hydrides BH4 and their deuterated species BD4 in a crystalline environment of alkali metals (M=Na, K). The solid state cases are particularly insightful as, in the B-H (or B-D) stretching region here considered, they exhibit many spectral features entire-ly due to anharmonic effects: two out of three in the IR spectrum and four out of six in the Raman spectrum. All IR and Raman active overtones and combination bands experimentally observed are correctly predicted with our approach. The effect of the adopted quantum-chemical model (DFT exchange-correlation functional/basis set) for the electronic structure calculations on the computed spectra is discussed and found to be significant, which suggests some special care is needed for the analysis of subtle spectral features.