Unified Diamond Hydride (UDH): A Co-Designed Lithium–Boron–Carbon–Nitrogen Framework with a Compressed Hydrogen Sublattice for Ambient-Pressure High-Temperature Superconductivity

We propose a materials concept for ambient-pressure high-temperature superconductivity: the Unified Diamond Hydride (UDH). The material is based on a single stoichiometry, Li2B2C2N2 ⋅ (H2)6 which combines a rigid diamond-like B–C–N framework, lithium atoms acting simultaneously as electron donors and internal compression agents, boron arranged in a periodic superlattice as a phonon amplifier, and a hydrogen sublattice geometrically correlated with the host tetrahedral network. The design targets a high hydrogenweighted electron–phonon coupling Λ𝐻 = 𝑁𝐻(𝐸𝐹 )⟨|𝑔𝐻|2⟩, a Van Hove singularity near the Fermi level, and a self-locking cage mechanism for metastability at ambient pressure. We provide a computational validation protocol, a synthesis strategy based on high-pressure assembly, removable magnesium prop species, and cryogenic decompression, and a characterization plan including isotope-effect control. If the material satisfies the target conditions—𝑃ext = 1 atm, phonon-stable, 𝜔log > 1200 K, 𝜆 > 1.5, high 𝑁 (𝐸𝐹 ), and 𝜆𝐻/𝜆 > 0.5—a superconducting transition temperature in the 200–300 K range may be expected. This proposal is speculative and intendedto stimulate systematic theoretical and experimental investigation.