 
Summary: Efficient localized basis set for quantum Monte Carlo calculations on condensed matter
D. Alfè1,2
and M. J. Gillan2
1Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, United Kingdom
2Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
(Received 11 June 2004; published 11 October 2004)
We present an efficient scheme for representing manybody wave functions in quantum Monte Carlo (QMC)
calculations. The scheme is based on B splines (blip functions), which consist of localized cubic splines
centered on the points of a regular grid. We show that blip functions are unbiased, systematically improvable,
and conveniently obtained from any standard planewave density functional theory (PWDFT) code, and
therefore provide a convenient and natural interface between PWDFT and QMC calculations. We present tests
on a 16atom system of Si in the tin structure, and on 2 and 8atom systems of MgO in the NaCl structure.
We show that already with such small systems the speedup of blip functions with respect to plane waves is
between one and two order of magnitudes, without compromising the accuracy.
DOI: 10.1103/PhysRevB.70.161101 PACS number(s): 71.10. w, 71.15. m, 71.27. a
The quantum Monte Carlo (QMC) technique1
is becom
ing one of the standard ways of studying condensed matter,
because its accuracy is generally better than that of widely
used techniques such as density functional theory (DFT). It
