Mechanical and Electronic Properties of XC(6) and XC(12)

A series of carbon-based superconductors XC(6) with high T(c) were reported recently. In this paper, based on the first-principles calculations, we studied the mechanical properties of these structures, and further explored the XC(12) phases, where the X atoms are from elemental hydrogen to calcium, except noble gas atoms. The mechanically- and dynamically-stable structures include HC(6), NC(6), and SC(6) in XC(6) phases, and BC(12), CC(12), PC(12), SC(12), ClC(12), and KC(12) in XC(12) phases. The doping leads to a weakening in mechanical properties and an increase in the elastic anisotropy. C(6) has the lowest elastic anisotropy, and the anisotropy increases with the atomic number of doping atoms for both XC(6) and XC(12). Furthermore, the acoustic velocities, Debye temperatures, and the electronic properties are also studied.