Highly-accurate quartic force fields for the prediction of anharmonic rotational constants and fundamental vibrational frequencies

• Quartic force fields of the highest level provide rotational constants to within, on average, 34 MHz experiment. Tetraatomic species with low anharmonicities can be within 20 MHz. These same methods vibrational frequencies 5.8 cm ?1 . The CcCR quartic field (QFF) methodology is capable computing B 0 and C 35 (0.14%) experiment for triatomic larger molecules at least two heavy atoms. Additionally, four or more atoms agree (0.12%) current test set. This work also supports previous claims that QFF produce fundamental a deviation less than 5.7 from Consequently, this approach augmenting complete basis set extrapolated energies treatments core electron correlation scalar relativity produces some most accurate rovibrational spectroscopic data available.