^{1}*Theory of Condensed Matter group, Cavendish Laboratory, University of Cambridge, J. J. Thomson Ave, Cambridge CB3 0HE, UK*

^{2}*Physical & Theoretical Chemistry Laboratory, South Parks Road, University of Oxford, Oxford OX1 3QZ, UK*

^{3}*Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge MA, USA*

Basis set superposition error (BSSE) in density-functional
calculations occurs when the extended Kohn-Sham orbitals are expanded
in localised basis sets, but is absent when a plane-wave basis is
used. Elimination of BSSE is essential for the accurate description of
intermolecular forces. Linear-scaling methods are formulated in terms
of local orbitals, making plane-waves an inappropriate choice of
basis. In this work the BSSE in linear-scaling methods is studied in
the context of hydrogen bonds. In particular it is shown that BSSE is
eliminated by optimizing the local orbitals *in situ* using a
systematic basis set equivalent to a set of plane-waves.

Last updated: 5 August 2010