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-P erdew and Becke-Lee, Yang, Parr) levels has been used to predict the g eometries, frequencies, and infrared intensities for H2O, HOO, CH4, an d C2H4. Large basis sets have been emplyed in this study. An extensive set of calculations was performed for H2O and HOO, whereas for CH4 an d C2H4 calculations were only done at the highest level. The calculate d 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.