Comment On the Accurate Theoretical Determination of Heats of Formation

Different theoretical approaches in determining heats of formation (DELTA-H(f)) at the chemical accuracy level (+/-kcal/mol) are commented on. We show that calculations at the MP4SDTQ/6-311 + + G(3df, 2p) level of molecular orbital theory reproduce experimental results best. Accurate determination of DELTA-H(f) also depends on the choice of working reactions. It is shown that, in a large number of cases, the additivity assumption of basis set extensions does not hold and that the quadratic configuration interaction QCISD(T) method does not lead to any significant improvement with respect To DELTA-H(f) obtained from the perturbative MP4SDTQ treatment