Wittenbrink Nils, Venghaus Florian, Williams David, Eisfeld Wolfgang
Theoretische Chemie, Universität Bielefeld, Postfach 100131, D-33501 Bielefeld, Germany.
J Chem Phys. 2016 Nov 14;145(18):184108. doi: 10.1063/1.4967258.
A new diabatization method is presented, which is suitable for the development of accurate high-dimensional coupled potential energy surfaces for use in quantum dynamics studies. The method is based on the simultaneous use of adiabatic wave function and energy data, respectively, and combines block-diagonalization and diabatization by ansatz approaches. It thus is called hybrid diabatization. The adiabatic wave functions of suitable ab initio calculations are projected onto a diabatic state space and the resulting vectors are orthonormalized like in standard block-diagonalization. A parametrized diabatic model Hamiltonian is set up as an ansatz for which the block-diagonalization data can be utilized to find the optimal model. Finally, the parameters are optimized with respect to the ab initio reference data such that the deviations between adiabatic energies and eigenvalues of the model as well as projected state vectors and eigenvectors of the model are minimized. This approach is particularly advantageous for problems with a complicated electronic structure where the diabatic state space must be of higher dimension than the number of calculated adiabatic states. This is an efficient way to handle problems with intruder states, which are very common for reactive systems. The use of wave function information also increases the information content for each data point without additional cost, which is beneficial in handling the undersampling problem for high-dimensional systems. The new method and its performance are demonstrated by application to three prototypical systems, ozone (O), methyl iodide (CHI), and propargyl (HCCCH).
提出了一种新的 diabatic 化方法，该方法适用于开发用于量子动力学研究的精确高维耦合势能面。该方法分别基于同时使用绝热波函数和能量数据，并通过假设方法结合块对角化和 diabatic 化。因此，它被称为混合 diabatic 化。将合适的从头算计算的绝热波函数投影到 diabatic 态空间，并且像在标准块对角化中一样对所得向量进行正交归一化。建立一个参数化的 diabatic 模型哈密顿量作为假设，利用块对角化数据来找到最优模型。最后，针对从头算参考数据对参数进行优化，以使绝热能量与模型的本征值之间以及投影态向量与模型的本征向量之间的偏差最小化。这种方法对于具有复杂电子结构的问题特别有利，其中 diabatic 态空间的维度必须高于计算的绝热态的数量。这是处理具有侵入态问题的有效方法，侵入态在反应体系中非常常见。波函数信息的使用还增加了每个数据点的信息含量而无需额外成本，这有利于处理高维系统的欠采样问题。通过应用于三个典型系统，臭氧（O₃）、碘甲烷（CH₃I）和丙炔基（HCCCH），展示了新方法及其性能。
