Extended hydrogen frameworks in nonmetallic superhydrides enabling 190 K superconductivity

Abstract

Extended hydrogen-rich frameworks stabilized under high pressure are essential for achieving high-temperature superconductivity in metal hydrides, where metal atoms contribute both charge and intrinsic precompression. In contrast, p-block nonmetal hydrides lack such extended hydrogenic connectivity. Here, using first-principles crystal structure search calculations, we identify three nitrogen-based superhydrides—NH₁₀, NH₁₁, and NH₁₂—each featuring a unique extended H sublattice: corrugated graphene-like hydrogen layers in NH₁₀, planar H${}_{16}$-ring sheets in NH₁₁, and a fully three-dimensional, densely connected H framework in NH₁₂. These structures are stabilized by ${{\mathrm{NH}}_4}^{+}$ units, which donate charge in a manner analogous to metal atoms in conventional metal superhydrides. Remarkably, NH₁₀ exhibits a superconducting critical temperature ($T_c$) of 190 K at 200 GPa, driven by strong electron–phonon coupling between H-1s states and low-frequency hydrogen-derived phonon modes—a mechanism notably distinct from that of hydrogen cages in LaH₁₀ and CaH₆. The predicted $T_c$ values of NH₁₁ and NH₁₂ also exceeds 130 K. Our work introduces a new paradigm for designing nonmetal superhydrides with structurally engineered hydrogenic frameworks.