High-Tc superconductivity in doped molecular superconductors of K4B8-xMxH32 (M = C, N) under high pressure

Stabilized and metallic light elements hydrides have provided a potential route to achieve the goal of room-temperature superconductors at moderate or ambient pressures. Here, we have performed systematic DFT theoretical calculations to examine the effects of different light elements C and N atoms doped in cubic K4B8H32 hydrides on the superconductivity at low pressures. As a result of various atoms substituting, we have found that metallic K4B8-xMxH32 (M = C, N) hydrides are dynamically stable at 50 GPa, band structures and density of states (DOS) indicate that sizeable T-c correlates with a high B-H DOS at the Fermi level. With the increasing of B atoms in K4B8-xMxH32 hydrides, the DOS values at Fermi level have been improved due to the delocalized electrons in B-H bonds, which result in strong electron-phonon coupling (EPC) interaction and increase the T-c from 19.04 to 77.07 K for KC2H8 and KB2H8 at 50 GPa. The NH4 unit in stable K4B7NH32 hydrides has weakened the EPC and led to low T-c value of 21.47 K. Our results suggest the light elements hydrides KB2H8 and K4B7CH32 could estimate high T-c values at 50 GPa, and the boron hydrides would be potential candidates to design or modulate hydrides superconductors with high T-c at moderate or ambient pressures.