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A BSSE-free second-order perturbation theory from Hermitian CHA-SCF Canonic Orbitals
  • Pedro Salvador Sedano,
  • Istvan Mayer
Pedro Salvador Sedano
Universitat de Girona
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Istvan Mayer
Research Centre for Natural Sciences, Hungarian Academy of Sciences
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Abstract

We present an alternative perturbational approach free of basis set superposition error (BSSE) within the framework of the Chemical Hamiltonian Approach (CHA). The new formulation (CHA-S-MP2) is based on canonic (and orthogonal) CHA orbitals obtained from a hermitized CHA Fock operator. The final expression shows a considerable simplification of the method as compared to the previous CHA-MP2 formalism. In the present formulation only two four-index transformations are necessary so that the computational cost of the CHA-S-MP2 calculation is just twice that of a conventional uncorrected MP2 calculation. Also, contrary to the counterpoise method, the computational cost doesn’t depend on the number of interacting fragments. Numerical full geometry optimizations of water and hydrogen fluoride dimers and potential energy surfaces for helium and argon dimers for several basis sets are presented. The present method is compared to both the counterpoise and previous CHA-MP2 BSSE correction schemes, showing a remarkable agreement between all three methods. However, the wrong behavior using the aug-cc-pVDZ basis set indicates that the present method is not as robust as the original non-hermitian CHA-MP2 formulation.

Peer review status:IN REVISION

29 Apr 2021Submitted to International Journal of Quantum Chemistry
30 Apr 2021Assigned to Editor
30 Apr 2021Submission Checks Completed
06 May 2021Reviewer(s) Assigned
15 Jun 2021Review(s) Completed, Editorial Evaluation Pending
15 Jun 2021Editorial Decision: Revise Minor