Quasi-atom bonds and high-pressure stability of α-Mn and Mn–H compounds

We investigate the high-pressure stability of α-Mn, a complex 29-atom structure that persists up to 165 GPa. While earlier studies linked its stability to competition between magnetic ordering and bonding in the half-filled d band, our calculations show that the magnetic moment collapses above ~55 GPa, pointing to alternative mechanisms. Using a well-demonstrated new bond model [1] that examines intrinsic electron localization, charge redistribution, and bonding strength between interstitial sites, we find that significant atom-interstitial interactions play the dominant role in stabilizing α-Mn under pressure. Extending this framework [2], we design novel Mn–H compound(s) using an experimental and extensive crystal structure search algorithm for a wide range of configurations, including the α-Mn structural motif, and compare their stability against known manganese hydrides across a broad pressure range. These results highlight the critical role of non-local chemistry in α-Mn structure and suggest new avenues for hydride design under extreme conditions.