Ground-state phase in the three-dimensional topological Dirac semimetal Na3Bi

By means of the first-principles calculations, we found that the early characterized 3D topological Dirac semimetal P6(3)/mmc-Na3Bi is dynamically unstable at the ground state due to the presence of the large imaginary phonon frequencies around the K point. Alternatively, our calculations suggested a new ground-state phase crystalizing in a P(3) over bar c1 structure with buckled graphite-like Na/Bi sheets, which is both energetically and dynamically stable. Moreover, the calculations also uncovered that the P(3) over bar c1 phase is a 3D topological Dirac semimetal, with exactly the same electronic states of the metastable P6(3)/mmc phase.