Prediction of diamond-like, metallic boron structures

► A generalized structure-decoration scheme was proposed based on current literatures on sp2 hybridized boron and applied to decoration of the sp3 backbone frameworks for prediction of new 3-dimensional boron crystals. ► The predicted boron crystals are metallic and have a much lower energy of formation than the known high-pressure boron phases. ► This study provides an explanation for the nonmetal-metal transition and the anomalous superconductivity of boron under high pressure. ► A mechanism that relaxes the intrinsic frustration of three-center bonding plays a unified role in both boron sheet and the predicted diamond-like boron.