Analytic Gradient for Density Functional Theory Based on the Fragment Molecular Orbital Method

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• 作者：Kurt R. Brorsen ; Federico Zahariev ; Hiroya Nakata ; Dmitri G. Fedorov ; Mark S. Gordon
• 刊名：Journal of Chemical Theory and Computation
• 出版年：2014
• 出版时间：December 9, 2014
• 年：2014
• 卷：10
• 期：12
• 页码：5297-5307
• 全文大小：636K
• ISSN：1549-9626

文摘

The equations for the response terms for the fragment molecular orbital (FMO) method interfaced with the density functional theory (DFT) gradient are derived and implemented. Compared to the previous FMO鈥揇FT gradient, which lacks response terms, the FMO鈥揇FT analytic gradient has improved accuracy for a variety of functionals, when compared to numerical gradients. The FMO鈥揇FT gradient agrees with the fully ab initio DFT gradient in which no fragmentation is performed, while reducing the nonlinear scaling associated with standard DFT. Solving for the response terms requires the solution of the coupled perturbed Kohn鈥揝ham (CPKS) equations, where the CPKS equations are solved through a decoupled Z-vector procedure called the self-consistent Z-vector method. FMO鈥揇FT is a nonvariational method and the FMO鈥揇FT gradient is unique compared to standard DFT gradients in that the FMO鈥揇FT gradient requires terms from both DFT and time-dependent density functional theory (TDDFT) theories.