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Published July 14, 2015 | Published
Journal Article Open

Accelerating wavefunction in density-functional-theory embedding by truncating the active basis set


Methods where an accurate wavefunction is embedded in a density-functional description of the surrounding environment have recently been simplified through the use of a projection operator to ensure orthogonality of orbital subspaces. Projector embedding already offers significant performance gains over conventional post-Hartree–Fock methods by reducing the number of correlated occupied orbitals. However, in our first applications of the method, we used the atomic-orbital basis for the full system, even for the correlated wavefunction calculation in a small, active subsystem. Here, we further develop our method for truncating the atomic-orbital basis to include only functions within or close to the active subsystem. The number of atomic orbitals in a calculation on a fixed active subsystem becomes asymptotically independent of the size of the environment, producing the required O(N^0) scaling of cost of the calculation in the active subsystem, and accuracy is controlled by a single parameter. The applicability of this approach is demonstrated for the embedded many-body expansion of binding energies of water hexamers and calculation of reaction barriers of S_N2 substitution of fluorine by chlorine in α-fluoroalkanes.

Additional Information

© 2015 AIP Publishing LLC. Received 2 April 2015; accepted 22 June 2015; published online 10 July 2015. The authors would like to thank David Tew, Gerald Knizia, Taylor Barnes, and Chris Taylor for helpful discussions. Analysis in this work was greatly helped through the use of the Gabedit suite. Some of this work was performed while F.R.M. was on sabbatical at Caltech; support for that visit from the Institute for Advanced Studies at the University of Bristol (University Research Fellowship) is gratefully acknowledged. We are grateful to EPSRC for funding for this work through research grants (Grant Nos. EP/K018965/1 and EP/J012742/1) and the Doctoral Training Grant. T.F.M. acknowledges support from the National Science Foundation CAREER Award under Grant No. CHE-1057112. All data from this work are held in an open-access repository.

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August 20, 2023
August 20, 2023