DFTB/PCM Applied to Ground and Excited State Potential Energy Surfaces
详细信息 查看全文
- 作者：Yoshio Nishimoto
- 刊名：Journal of Physical Chemistry A
- 出版年：2016
- 出版时间：February 11, 2016
- 年：2016
- 卷：120
- 期：5
- 页码：771-784
- 全文大小：637K
- ISSN：1520-5215
文摘
Accounting for solvent effects in quantum chemical calculations is vital for the accurate description of potential energy surfaces in solution. In this study, we derive a formulation of the analytical first-order geometrical derivative of ground- and excited-state energies within the time-dependent density-functional tight-binding (TD-DFTB) method with the polarizable continuum model (PCM), TD-DFTB/PCM. The performance of this is then evaluated for a series of halogen-exchange SN2 reactions. DFTB/PCM reproduces DFT results well for isolated monohalogenated methanes, but its agreement for transition structures significantly depends on the halogen element. The performance of TD-DFTB/PCM is evaluated for the excited-state intramolecular proton transfer (ESIPT) reaction of 3-hydroxyflavone (3HF) in ethanol. TD-DFTB/PCM reproduces the barrier height of the ESIPT reaction in terms of geometry and energy relatively well, but it fails to reproduce the experimental absorption and fluorescence energies as a consequence of the absence of long-range corrections. Computational timings with and without PCM show that the additional cost of PCM for C500H502 is only 10% greater than the corresponding calculation in vacuum. Furthermore, the potential applications of TD-DFTB/PCM are highlighted by applying it to a double-stranded DNA complexed with dye (PDB ID 108D). We conclude that TD-DFTB/PCM single-point calculations and geometry optimizations for systems consisting of more than 1000 and 500 atoms, respectively, is now manageable and that properties predicted with TD-DFTB must be interpreted with care.