CODECS 2013 Workshop
San Lorenzo de El Escorial, Madrid, 18th –22nd April, 2013
Basis set dependence using DFT/B3LYP calculations to model the
Raman spectrum of thymine
J. Bielecki a, E. Lipiecb, B.R Woodc, W.M. Kwiatekb
a
National Centre for Nuclear Research, Świerk Computing Centre Project, ul. Andrzeja Sołtana
7 05-400 Otwock, Świerk, Poland
b
The Henryk Niewodniczański Institute of Nuclear Physics, Polish Academy of Sciences, ul.
Radzikowskiego 152, 31-342 Kraków, Poland
c
School of Chemistry, Monash University, Victoria 3800, Australia
jakub.bielecki@ncbj.gov.pl
Raman spectroscopy (including Surface Enhanced Raman Spectroscopy (SERS) and Tip
Enhanced Raman Spectroscopy (TERS)) is a highly promising experimental method for
investigations of biomolecule damage induced by ionizing radiation. However, proper
interpretation of changes in experimental spectra for complex systems is often difficult or
impossible, thus Raman spectra calculations from Density Functional Theory (DFT) provide an
invaluable tool as an additional layer of understanding of underlying processes. There are many
works that address the problem of basis set dependence for energy and bond length
consideration, nevertheless there is still lack of consistent research on basis set influence on
Raman spectra intensities for biomolecules. This study fills this gap by investigating of the
influence of basis set choice for the interpretation of Raman spectra of the thymine molecule
calculated using the DFT/B3LYP framework and comparing these results with experimental
spectra. Among 19 selected Pople’s basis sets the best agreement was achieved using 6-31+(d,p),
6-31++(d,p) and 6-11++G(d,p) sets. Adding diffuse functions or polarized functions for small
basis set or use of a medium or large basis set without diffuse or polarized functions is not
sufficient to reproduce Raman intensities correctly. The introduction of the diffuse functions (++)
on hydrogen atoms is not necessary for gas phase calculations. This work serves as benchmark
for further research into DNA by means of ab-initio calculations and Raman spectroscopy.
Acknowledgments
This work was supported by the EU and MSHE grant nr POIG.02.03.00-00-013/09. The
research was also partially supported by PL-Grid project.