The correlation consistent Composite Approach: Efficient thermochemistry across the periodic table

AEI 46

Nathan DeYonker, ndeyonk@unt.edu, Angela K. Wilson, akwilson@unt.edu, and Thomas Cundari, tomc@unt.edu. Department of Chemistry, University of North Texas, Box 305070, Denton, TX 76203-5070
Our labs have implemented a new ab initio composite method called the correlation consistent composite approach (ccCA). By mainly employing MP2 computations which are extrapolated to the CBS limit, ccCA is a cost-effective alternative to large basis set coupled cluster methods such as the model chemistry of Dixon, Feller, Peterson and co-authors, as well as the Wn methods of Martin and co-workers. The ccCA also eschews the types of empirical corrections necessary for the success of the Gaussian-n or Gn model chemistries. With a 0.97 kcal mol^-1 mean absolute deviation when applied to the G3/99 test set of 376 energies, the ccCA achieves a level of accuracy comparable or better to the G3X model chemistry for main group systems. The Gn and Wn methods have shown a dramatic inability to model properties of certain types of alkali and alkaline earth metal complexes, yet ccCA has been proven to be flexible enough to describe these compounds accurately. The ccCA method has also been successfully adapted to compute energies of transition-metal systems, and the thermochemical accuracy is similar to large basis set coupled cluster model chemistries.