Excitation Energies of Canonical Nucleobases Computed by Multiconfigurational Perturbation Theories

Christian Wiebeler, Veniamin Borin, Adalberto Vasconcelos Sanchez de Araújo, Igor Schapiro*, Antonio Carlos Borin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


In this computational work, we assessed the performance of ab initio multireference (MR) methods for the calculation of vertical excitation energies of five nucleobases: adenine, guanine, cytosine, thymine and uracil. In total, we have studied 38 singlet and 30 triplet excited states. Where possible we used the multireference configuration interaction (MRCI) method as a reference for various flavors of multireference perturbation theory to second order. In particular, we have benchmarked CASPT2, NEVPT2 and XMCQDPT2. For CASPT2, we have analyzed the single-state, multistate (MS) and extended MS variants. In addition, we have assessed the effect of the ionization potential electron affinity (IPEA) shift. For NEVPT2, we have used the partially and the strongly contracted variants. Further, we have tested the commonly used RI-CC2, RI-ADC2 and EOM-CCSD methods. Generally, we observe the following trends for singlet excited states: NEVPT2 is the closest MR method to MRCISD+Q, closely followed by CASPT2 with the default IPEA shift. The same trend is observed for triplet states, although NEVPT2 and CASPT2-IPEA are getting closer. Interestingly, the n, π* singlet excited states were described more accurately than π, π* excited states, while for triplet states the trend is inverted except for NEVPT2. This work is an important benchmark for future photochemical investigations.

Original languageAmerican English
Pages (from-to)888-902
Number of pages15
JournalPhotochemistry and Photobiology
Issue number3
StatePublished - 1 May 2017

Bibliographical note

Publisher Copyright:
© 2017 The American Society of Photobiology


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