Stabilizing a novel hexagonal Ru2C through Lifshitz transition under pressure

A new type of heavy transition metal carbide (TMC), Ru2C with a space group of p3 - m1(164) was synthesized experimentally at high pressurehigh temperature [J Phys. Condens. Matter. 2012 Sep 12; 24(36): 362202.] and it was consequently quenched to ambient condition. We have carried out the dynamical stability study, which reveals the instability at ambient condition. The effect of pressure has been taken into consideration in order to stabilize as the reported synthesizing condition. We have found that it can be stabilized from 30 GPa to 110 GPa. The stronger 4d -2p hybridization and the formation of a cage like Fermi surface do impact the stability and also illustrates a Lifshitz transition. We have also found a mixed 4d-2p bands crossing the Fermi level form a Fermi surface piece at {\Gamma} point under pressure. The freshly appearing bands provide a tunnel for quantum transportation and it reduces the density of states at Fermi level, which further stabilizes the lattice under pressure.