First-principles study on the conventional superconductivity of N-doped fcc-LuH3

Recently, room-temperature superconductivity has been reported in a nitrogen-doped lutetium hydride at near-ambient pressure [Dasenbrock-Gammon et al., Nature 615, 244 (2023)]. The superconducting properties might arise from Fm 3 ̄ m-LuH3−δNε. Here, we systematically study the phase diagram of Lu–N–H at 1 GPa using first-principles calculations, and we do not find any thermodynamically stable ternary compounds. In addition, we calculate the dynamic stability and superconducting properties of N-doped Fm 3 ̄ m-LuH3 using the virtual crystal approximation (VCA) and the supercell method. The R3m-Lu2H5N predicted using the supercell method could be dynamically stable at 50 GPa, with a Tc of 27 K. According to the VCA method, the highest Tc is 22 K, obtained with 1% N-doping at 30 GPa. Moreover, the doping of nitrogen atoms into Fm 3 ̄ m-LuH3 slightly enhances Tc, but raises the dynamically stable pressure. Our theoretical results show that the Tc values of N-doped LuH3 estimated using the Allen–Dynes-modified McMillan equation are much lower than room temperature.