Optimization of orbital-specific virtuals in local Møller-Plesset perturbation theory
We present an orbital-optimized version of our orbital-specific-virtuals second-order Møller-Plesset perturbation theory (OSV-MP2). The OSV model is a local correlation ansatz with a small basis of virtual functions for each occupied orbital. It is related to the Pulay–Saebø approach, in which domains of virtual orbitals are drawn from a single set of projected atomic orbitals; but here the virtual functions associated with a particular occupied orbital are specifically tailored to the correlation effects in which that orbital participates. In this study, the shapes of the OSVs are optimized simultaneously with the OSV-MP2 amplitudes by minimizing the Hylleraas functional or approximations to it. It is found that optimized OSVs are considerably more accurate than the OSVs obtained through singular value decomposition of diagonal blocks of MP2 amplitudes, as used in our earlier work. Orbital-optimized OSV-MP2 recovers smooth potential energy surfaces regardless of the number of virtuals. Full optimization is still computationally demanding, but orbital optimization in a diagonal or Kapuy-type MP2 approximation provides an attractive scheme for determining accurate OSVs.
© 2012 American Institute of Physics. Received 15 November 2011; accepted 6 March 2012; published online 27 March 2012. This work was begun during a visit of one of us (Y.K.) to Bristol in 2010. Y.K. acknowledges support for this work from Ministry of Education, Culture, Sports, Science and Technology-Japan (MEXT) via the Young Scientists (B) (Grant No. 21750028) G.K.-L.C. acknowledges support for this work from the U.S. Department of Energy (DOE), Office of Science via Award No. DE-FG02-07ER46432, as well as support from the David and Lucile Packard foundation.
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