Hydrogen-rich superconductors: efficient estimations of T_c from electronic properties

In hydrogen-rich materials, electron-phonon superconductivity can appear at high critical temperatures (T_c), reaching values beyond 200K. Despite this clear advantage, they usually need megabar pressures to be stabilized, and the theoretical prediction of new compounds at ambient conditions is slowed down by expensive estimations of T_c. In this work, we show how first estimations can be obtained only from ab initio electronic properties, dramatically reducing the computational cost. We identify two key characteristics of high-T_c hydrogen-rich superconductors: (i) a density of states (DOS) at the Fermi energy with an important relative hydrogen contribution, and (ii) a high delocalization of electrons in the hydrogen bonds, that spans through the periodic lattice. We propose descriptors coming from the electron localization function to quantify the latter condition and, along with the DOS-derived descriptor, permit to find a correlation with the critical temperature. Finally, we present TcESTIME, a program that estimates T_c in only a couple of seconds after a standard DFT calculation. This opens up the possibility of doing a high-throughput screening of candidate superconductors, and focus expensive computational and experimental efforts on promising structures.