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Exchange-correlation energy and the phase diagram of Si D. Alfe`1,2
 

Summary: Exchange-correlation energy and the phase diagram of Si
D. Alfe`1,2
and M. J. Gillan2
1
Earth Sciences Department, University College London, Gower Street, London WC1E 6BT, United Kingdom
2
Physics and Astronomy Department, University College London, Gower Street, London WC1E 6BT, United Kingdom
Received 17 July 2002; revised manuscript received 14 August 2003; published 24 November 2003
Previous first-principles calculations of the melting properties of Si, based on the local-density approxima-
tion LDA for electronic exchange-correlation energy, underpredict the melting temperature by 20 %. We
present new first-principles results indicating that a large part of this problem is due to noncancellation of
exchange-correlation errors between the semiconducting solid and the metallic liquid. It is shown that other
sources of error, particularly those due to system size and Brillouin-zone sampling, can be made negligible.
The same LDA errors cause an underprediction of the pressure of the diamond-Si beta-tin-Si transition. The
generalized-gradient approximation considerably improves both features of the Si phase diagram.
DOI: 10.1103/PhysRevB.68.205212 PACS number s : 64.70.Dv, 81.30.Dz, 71.15.Pd
The long-standing ambition of calculating phase diagrams
from first-principles quantum mechanics has become a real-
ity in the last 10 years.1­4
A key stimulus to the recent de-

  

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

 

Collections: Physics; Geosciences