Alternative formulation of explicitly correlated thirdorder MøllerPlesset perturbation theory
Abstract
The secondorder wave operator in the explicitly correlated wave function theory has been newly defined as an extension of the conventional s and pwave (SP) ansatz (also referred to as the FIXED amplitude ansatz) based on the linkeddiagram theorem. The newly defined secondorder wave operator has been applied to the calculation of the F12 correction to the thirdorder manybody perturbation (MP3) energy. In addition to this new wave operator, the F12 correction with the conventional firstorder wave operator has been derived and calculated. Among three components of the MP3 correlation energy, the particle ladder contribution, which has shown the slowest convergence with respect to the basis set size, is fairly ameliorated by employing these F12 corrections. Both the newly defined and conventional formalisms of the F12 corrections exhibit a similar recovery of over 90% of the complete basis set limit of the particle ladder contribution of the MP3 correlation energy with a triplezeta quality basis set for the neon atom, while the amount is about 75% without the F12 correction. The corrections to the ring term are small but the corrected energy has shown similar recovery as the particle ladder term. The hole ladder term has shown a rapid convergence even without the F12 corrections. Owing to these balanced recoveries, the deviation of the total MP3 correlation energy from the complete basis set limit has been calculated to be about 1 kcal/mol with the triplezeta quality basis set, which is more than five times smaller than the error without the F12 correction.
 Publication:

Molecular Physics
 Pub Date:
 September 2013
 DOI:
 10.1080/00268976.2013.793846
 Bibcode:
 2013MolPh.111.2516O
 Keywords:

 F12 cusp conditions;
 MP3F12;
 rational generator;
 SP ansatz