The α–β phase boundary of elemental boron

Abstract

The phase boundary between α- and β-rhombohedral boron is theoretically determined based on first-principles Gibbs free energy calculations. For the free energy of β-boron, an adjustable scaling parameter was introduced to correct the underestimate of the phonon frequencies of β-boron due to omission of partial occupancy. We show that the adjusted α–β phase boundary agrees well with two recent experimental reports.