Multimode quantum dynamics using Gaussian wavepackets: The Gaussian-based multiconfiguration time-dependent Hartree (G-MCTDH) method applied to the absorption spectrum of pyrazine

I Burghardt, Kousik Giri, Graham Worth

Research output: Contribution to journalArticle

126 Citations (Scopus)

Abstract

The Gaussian-based multiconfiguration time-dependent Hartree (G-MCTDH) method is applied to calculate the S-2(pi pi(*)) absorption spectrum of the pyrazine molecule, whose diffuse structure results from the ultrafast nonadiabatic dynamics at the S-2-S-1 conical intersection. The 24-mode second-order vibronic-coupling model of Raab [J. Chem. Phys. 110, 936 (1999)] is employed, along with 4-mode and 10-mode reduced-dimensional variants of this model. G-MCTDH can be used either as an all-Gaussian approach or else as a hybrid method using a partitioning into primary modes, treated by conventional MCTDH basis functions, and secondary modes described by Gaussian particles. Comparison with standard MCTDH calculations shows that the method converges to the exact result. The variational, nonclassical evolution of the moving Gaussian basis is a key element in obtaining convergence. For high-dimensional systems, convergence is significantly accelerated if the method is employed as a hybrid scheme.
Original languageEnglish
Pages (from-to)174104
Number of pages1
JournalJournal of Chemical Physics
Volume129
Issue number17
DOIs
Publication statusPublished - 1 Nov 2008

Keywords

  • organic compounds
  • variational techniques
  • ultraviolet spectra
  • visible spectra
  • vibronic states
  • infrared spectra

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