New ab initio approach for high pressure systems with application to a new high-pressure phase for boron: perturbative momentum-space potentials

Through the use of perturbation theory, in this work we develop a method which allows for a substantial reduction in the size of the plane-wave basis used in density-functional calculations. This method may be used for both pseudopotentials and all-electron calculations and is particularly beneficial in the latter case. In all cases, the approach has the advantage of allowing accurate predictions of transferability errors for any environment. Finally, this method can be easily implemented into conjugate gradient techniques and it is therefore computationally efficient. In this work, we apply this method to study high pressure phases of boron. We find that boron undergoes a phase transition from the icosahedral family to the alpha-orthorhombic structure, both of which are semiconducting. The alpha-orthorhombic structure has lower energy than traditional mono-atomic structures, which supports the assertion that the metallic, and hence superconducting phase, for boron is much more complicated than a simple mono-atomic crystal. Moreover, we argue that the beta-orthorhombic structure could be a candidate for the superconducting phase of boron.