title: High-accuracy extrapolated ab initio thermochemistry. III. Additional improvements and overview.
abstract: Effects of increased basis-set size as well as a correlated treatment of the diagonal Born-Oppenheimer approximation are studied within the context of the high-accuracy extrapolated ab initio thermochemistry (HEAT) theoretical model chemistry. It is found that the addition of these ostensible improvements does little to increase the overall accuracy of HEAT for the determination of molecular atomization energies. Fortuitous cancellation of high-level effects is shown to give the overall HEAT strategy an accuracy that is, in fact, higher than most of its individual components. In addition, the issue of core-valence electron correlation separation is explored; it is found that approximate additive treatments of the two effects have limitations that are significant in the realm of <1 kJ mol(-1) theoretical thermochemistry.
authors: Institut für Physikalische Chemie, Universität Mainz, Mainz, Germany.
authors: Michael E
authors: ME
authors: Harding
authors: Juana
authors: J
authors: Vázquez
authors: Branko
authors: B
authors: Ruscic
authors: Angela K
authors: AK
authors: Wilson
authors: Jürgen
authors: J
authors: Gauss
authors: John F
authors: JF
authors: Stanton