Accurate ab Initio Quartic Force Fields and Thermochemistry of FNO and ClNO

The quartic force fields of FNO and ClNO have been computed at the CCSD(T)/cc-pVTZ level. Using an “augmented” basis set dramatically improves results for FNO but has no significant effect for ClNO. The computed force field for FWO yields harmonic frequencies and fundamentals in excellent agreement experiment. Overall, the force fields proposed in the present work are probably the most reliable ones published for these molecules. Total atomization energies have been computed using basis sets of spdfg : our best estimates are DO = 208.5 f 1 and 185.4 f 1 kcaymol for FNO and CINO, respectively. computed value for FNO suggests a problem with the established experimental heat of formation. tables in JANAF style at 100-2000 K are presented for both FNO and ClNO.