Comparison of methods for the calculation of phase stability in silicon

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Abstract
Calculations of the zero-temperature energy differences between the bcc, fcc, and hcp phases of compressed silicon are reported using the ab initio pseudopotential method, the linear-muffin-tin-orbitals (LMTO) method with all electrons treated self-consistently, and the LMTO method with the core replaced by the pseudopotential used in the first approach. The lattice-energy differences obtained by the three techniques are found to be in mRy quantitative agreement. It is concluded that the pseudopotential approximation is quite accurate for moderately compressed silicon, and that the atomic-sphere approximation of the LMTO method does not significantly alter conclusions about the relative phase stability amongst the high-symmetry phases of this material.