Comparison of DFT methods for molecular structure and vibrational spectrum of pyrimidine molecule

Neha Shukla, Achchhe Lal, Vipi

Abstract

The effect of ten chosen Density Functional Theory (DFT) methods at various basis sets for predicting the molecular structure, vibrational frequencies and infrared intensities of pyrimidine molecule has been investigated. The exchange functionals DFT employed in this study include local (SVWN), Gradient corrected (BLYP, PW91PW91, mPWPW91, G96LYP, PBEPBE) and hybrid (B3LYP, B3PW91, mPW1LYP, mPW1PW91) and basis sets include Pople basis sets 6-311G(d,p), 6-311++G(d,p), 6-311G(2d,2p), 6-311++G(2d,2p), 6-311G(3d,3p) 6- 311++G(3d,3p), 6-311G(2df,2pd) 6-311++G(2df,2pd), 6-311G(3df,3pd), 6-311++G(3df,3pd) and Dunning's correlation-consistent basis sets cc-pVDZ, aug-cc-pVDZ, cc-pVTZ and aug-cc-pVTZ. The results are compared with the available experimental data in the gas phase. Bond distances and bond angles computed at the PBEPBE/6-311G (3df, 3pd) level are in good agreement with the available experimental data. The results also indicate that for the vibrational spectrum of pyrimidine, B3LYP/6-311++G(d,p) result shows a good agreement with the experimental results than other DFT methods.