What Is the Best DFT Functional for Vibronic Calculations? A Comparison of the Calculated Vibronic Structure of the S1鈥揝0 Transition of Phenylacetylene with Cavity Ringdown Band
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- 作者：Gary V. Lopez ; Chih-Hsuan Chang ; Philip M. Johnson ; Gregory E. Hall ; Trevor J. Sears ; Beatrice Markiewicz ; Mariana Milan ; Alexey Teslja
- 刊名：The Journal of Physical Chemistry A
- 出版年：2012
- 出版时间：June 28, 2012
- 年：2012
- 卷：116
- 期：25
- 页码：6750-6758
- 全文大小：311K
- 年卷期：v.116,no.25(June 28, 2012)
- ISSN：1520-5215
文摘
The sensitivity of vibronic calculations to electronic structure methods and basis sets is explored and compared to accurate relative intensities of the vibrational bands of phenylacetylene in the S1(A1B2) 鈫?S0(X1A1) transition. To provide a better measure of vibrational band intensities, the spectrum was recorded by cavity ringdown absorption spectroscopy up to energies of 2000 cm鈥? above the band origin in a slit jet sample. The sample rotational temperature was estimated to be about 30 K, but the vibrational temperature was higher, permitting the assignment of many vibrational hot bands. The vibronic structure of the electronic transition was simulated using a combination of time-dependent density functional theory (TD-DFT) electronic structure codes, Franck鈥揅ondon integral calculations, and a second-order vibronic model developed previously [Johnson, P. M.; Xu, H. F.; Sears, T. J. J. Chem. Phys.2006, 125, 164331]. The density functional theory (DFT) functionals B3LYP, CAM-B3LYP, and LC-BLYP were explored. The long-range-corrected functionals, CAM-B3LYP and LC-BLYP, produced better values for the equilibrium geometry transition moment, but overemphasized the vibronic coupling for some normal modes, while B3LYP provided better-balanced vibronic coupling but a poor equilibrium transition moment. Enlarging the basis set made very little difference. The cavity ringdown measurements show that earlier intensities derived from resonance-enhanced multiphoton ionization (REMPI) spectra have relative intensity errors.