Electronic Structure Theory of H 3 S: Plane‐Wave‐Like Valence States, Density‐of‐States Peak and Its Guaranteed Proximity to the Fermi Level

ABSTRACT Superconductivity in sulfur superhydride H 3 S under extreme pressures has been explained theoretically, but it requires a peaked concentration of the electronic density of states (DOS), which has been found in first‐principles calculations. The mechanism of this peak formation, though vital for its high transition temperature, has however remained obscure. We address this problem through detailed analysis of the first‐principles electronic wave functions. The valence wave functions are