Electron correlation and the phase diagram of Si
  Previous first-principles calculations of the melting properties of Si, based on the local-density approximation (LDA) for electronic exchange-correlation energy, under-predict the melting temperature by ~ 20%. We present new first-principles results demonstrating that this problem is due to non-cancellation 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 largely corrects both features of the Si phase diagram. 
D. Alf\`e(1,2) and M. J. Gillan (2) ((1) Dept. of Geological Sciences,   University College London (2) Dept. of Physics and ...