PREDICTION OF INFRARED INTENSITIES BY USING DENSITY-FUNCTIONAL THEORY - APPLICATIONS TO H2O, HOO, CH4, AND C2H4

Density functional theory at the local and gradient-corrected (Becke-Perdew and Becke-Lee, Yang, Parr) levels has been used to predict the geometries, frequencies, and infrared intensities for H2O, HOO, CH4, and C2H4. Large basis sets have been emplyed in this study. An extensive set of calculations was performed for H2O and HOO, whereas for CH4 and C2H4 calculations were only done at the highest level. The calculated infrared intensities at the BP/TZVPD level are I-1 = 1.8, I-2 = 68.9, and I-3 = 49.9 km/mol for H2O; I-1 = 11.8, I-2 = 33.8, and I-3 = 16.8 km/mol for HOO; I(t(1u)-str) = 60.3 and I(t(1u)-bend) = 37.0 km/mol for CH4; and I(v(7))= 96.7, I(v(9)) = 19.3, I(V-10) = 0.2, I(v(11)) = 17.6, and I(v(12)) = 9.3 km/mol for C2H4.