Explicitly correlated RMP2 for high-spin open-shell reference states
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- 16 April 2008
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 128 (15), 154103
- https://doi.org/10.1063/1.2889388
Abstract
We present an explicitly correlated version of the high-spin open-shell RMP2 method. The theory is derived in a unitarily invariant form, which is suitable for the insertion of local approximations. It is demonstrated that the rapid basis set convergence of closed-shell MP2-F12 is also achieved in RMP2-F12, and similar Ansätze and approximations can be employed. All integrals are computed using efficient density fitting approximations, and many-electron integrals are avoided using resolution of the identity approximations. The performance of the method is demonstrated by benchmark calculations on a large set of ionization potentials, electron affinities and atomization energies. Using triple-zeta basis sets RMP2-F12 yields results that are closer to the basis set limit than standard RMP2 with augmented quintuple-zeta basis sets for all properties. Different variants of perturbative corrections for the open-shell Hartree–Fock treatment are described and tested.Keywords
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