Ka. Peterson et al., BENCHMARK CALCULATIONS WITH CORRELATED MOLECULAR WAVE-FUNCTIONS .3. CONFIGURATION-INTERACTION CALCULATIONS ON 1ST ROW HOMONUCLEAR DIATOMICS, The Journal of chemical physics, 99(12), 1993, pp. 9790-9805
Using correlation consistent basis sets from double through quintuple
zeta quality, potential energy functions have been calculated for the
electronic ground states of the first row homonuclear diatomic molecul
es B2, C2, N2, O2 and F2 using single and double excitation configurat
ion interaction (HF + 1 + 2, GVB + 1 + 2, and CAS + 1 + 2) wave functi
ons. Spectroscopic constants have been calculated for each species and
compared to experiment. The dependence of the calculated spectroscopi
c constants on systematic extensions of the one-particle basis set are
, in general, found to be very regular. By fitting the directly calcul
ated values with a simple exponential function, accurate estimates of
the complete basis set (CBS) limit for E(e), D(e), and r(e) have been
obtained for each level of theory. The estimated CBS limits are compar
ed to the available experimental results, and the intrinsic errors ass
ociated with each theoretical method are discussed. In addition, the a
ccuracy of the internally contracted CAS + 1 + 2 method is compared to
conventional uncontracted calculations using large basis sets. For B2
, a full CI calculation have been carried out for D(e) with the correl
ation consistent double zeta basis set and is compared to the CAS + 1
+ 2 method using both a supermolecule and separated atom approach for
the dissociated limit.