Direct Atomic-Orbital-Based Relativistic Two-Component Linear Response Method for Calculating Excited-State Fine Structures

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• 作者：Franco Egidi ; Joshua J. Goings ; Michael J. Frisch ; Xiaosong Li
• 刊名：Journal of Chemical Theory and Computation
• 出版年：2016
• 出版时间：August 9, 2016
• 年：2016
• 卷：12
• 期：8
• 页码：3711-3718
• 全文大小：375K
• 年卷期：0
• ISSN：1549-9626

文摘

In this work, we present a linear-response formalism of the complex two-component Hartree–Fock Hamiltonian that includes relativistic effects within the Douglas–Kroll–Hess and the Exact-Two-Component frameworks. The method includes both scalar and spin relativistic effects in the variational description of electronic ground and excited states, although it neglects the picture-change and explicit spin–orbit contributions arising from the two-electron interaction. An efficient direct formalism of solving the complex two-component response function is also presented in this work. The presence of spin–orbit couplings in the Hamiltonian and the two-component nature of the wave function and Fock operator allows the computation of excited-state zero-field splittings of systems for which relativistic effects are dominated by the one-electron term. Calculated results are compared to experimental reference values to assess the quality of the underlying approximations. The results show that the relativistic two-component linear response methods are able to capture the excited-state zero-field splittings with good agreement with experiments for the systems considered here, with all approximations exhibiting a similar performance. However, the error increases for heavy elements and for states of high orbital angular momentum, suggesting the importance of the two-electron relativistic effect in such situations.