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Diamond and -tin structures of Si studied with quantum Monte Carlo calculations and M. J. Gillan2
 

Summary: Diamond and -tin structures of Si studied with quantum Monte Carlo calculations
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
M. D. Towler and R. J. Needs
Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
(Received 1 July 2004; published 3 December 2004)
We have used diffusion quantum Monte Carlo (DMC) calculations to study the pressure-induced phase
transition from the diamond to -tin structure in silicon. The calculations employ the pseudopotential tech-
nique and systematically improvable B-spline basis sets. We show that in order to achieve a precision of 1 GPa
in the transition pressure the noncanceling errors in the energies of the two structures must be reduced to
30 meV/atom. Extensive tests on system size errors, nonlocal pseudopotential errors, basis-set incompleteness
errors, and other sources of error, performed on periodically repeated systems of up to 432 atoms, show that all
these errors together can be reduced to well below 30 meV/atom. The calculated DMC transition pressure is
about 3­4 GPa higher than the accepted experimental range of values, and we argue that the discrepancy may
be due to the fixed-node error inherent in DMC techniques.
DOI: 10.1103/PhysRevB.70.214102 PACS number(s): 64.70. p, 71.15. m
I. INTRODUCTION
The importance of the quantum Monte Carlo technique

  

Source: Alfè, Dario - Departments of Earth Sciences & Physics and Astronomy, University College London

 

Collections: Physics; Geosciences