First-principles prediction of a metastable crystalline phase of Ga withCmcmsymmetry

Abstract

We report on evidence for the existence of an unknown metastable crystalline phase of gallium by the combination of classical molecular-dynamics (MD) simulations and density-functional theory (DFT) calculations. The MD simulations, based on a modified embedded-atom potential, reveal the unknown crystalline form through a first-order phase transition originating from the $Cmca$ symmetric $\ensuremath{\alpha}\text{-Ga}$ phase under hydrostatic tension. Subsequently, the DFT calculations using two different generalized-gradient approximation functionals are employed to verify its stability and determine its electronic structure. The structure of the orthorhombic phase is described by symmetry group $Cmcm$ and shows a dimer arrangement resembling the $\ensuremath{\alpha}\text{-Ga}$ phase. A first-order phase transition from $\ensuremath{\alpha}\text{-Ga}$ to the unknown phase is estimated to occur at $\ensuremath{-}1.3\text{ }\text{GPa}$.