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Carbides have attracted much attention owing to their interesting physical and chemical properties.Here,we systematically investigated global energetically stable structures of BeC2 in the pressure range of 0–100 GPa using a first-principles structural search.A transition from the ambient-pressure α-phase to the high-pressure β-phase was theoretically predicted.Chemical bonding analysis revealed that the predicted phase transition is associated with the transformation from sp2 to sp3 C-C hybridization.The electrical conductivity of the high-pressure phase changed from a metal(α-phase) to a narrow bandgap semiconductor(β-phase),and the β-phase had an inverted band structure with positive pressure dependence.Interestingly,the β-phase was a topological insulator with the metallic surface states protected by the time-reversal symmetry of the crystal.The results indicate that pressure modulates the electronic band structure of BeC2,which is an important finding for fundamental physics and for a wide range of potential applications in electronic devices.