{"paper":{"title":"H$_2$-Like Units and Pressure-Tunable High-$T_\\mathrm{c}$ Superconductivity in NaH$_6$","arxiv_id":"2610.17148","primary_cat":"cond-mat.supr-con","submitted_at":"2026-10-12T17:28:46+00:00","version_compiled":"v1"},"notice":"Every quoted sentence is the authors' text from the arXiv listing abstract. Labels and probabilities are the outputs of classifier-1.13.0 on the question bank abstract-p1-20260923, exactly as returned. No sentence in this record was written by a language model.","schema":"pith.compiled-record/v0","status":"compiled","abstract":{"source":"arXiv listing abstract v1","sentences":[{"i":0,"p":1.0,"id":"s0","own":false,"role":"background","text":"Hydrogen-rich materials offer a route to high-temperature conventional superconductivity, but often require extreme pressures.","hedge":{"p":0.85,"label":"asserted"},"own_p":0.04,"main_claim_p":0.03,"quantitative":false,"quantitative_p":0.08,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.0,"background":1.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.0}},{"i":1,"p":1.0,"id":"s1","own":true,"role":"contribution","text":"Here we report a first-principles study of NaH$_6$, identified in our large-scale hydride search and independently predicted in a subsequent high-throughput study.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.88,"main_claim_p":0.05,"quantitative":false,"quantitative_p":0.08,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":1.0,"interpretation":0.0}},{"i":2,"p":0.97,"id":"s2","own":true,"role":"result","text":"Several phases compete, with $R\\bar{3}m$ and $Pm\\bar{3}m$ dominant over broad pressure ranges.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.79,"main_claim_p":0.04,"quantitative":false,"quantitative_p":0.36,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.97,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.03,"interpretation":0.0}},{"i":3,"p":1.0,"id":"s3","own":true,"role":"result","text":"The $R\\bar{3}m$ phase remains dynamically stable down to 10 GPa, where its calculated $T_\\mathrm{c}$ is 34 K, rising to 99 K at 50 GPa.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.92,"main_claim_p":0.11,"quantitative":true,"quantitative_p":0.99,"role_probabilities":{"gap":0.0,"method":0.0,"result":1.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.0}},{"i":4,"p":1.0,"id":"s4","own":true,"role":"result","text":"Cubic $Pm\\bar{3}m$ becomes thermodynamically competitive at higher pressures and reaches a calculated $T_\\mathrm{c}$ of 230 K at 50 GPa, decreasing only weakly upon further compression.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.88,"main_claim_p":0.23,"quantitative":true,"quantitative_p":0.99,"role_probabilities":{"gap":0.0,"method":0.0,"result":1.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.0}},{"i":5,"p":0.79,"id":"s5","own":true,"role":"result","text":"Molecular dynamics and phonon-renormalization calculations support structural persistence over the sampled timescale and indicate relatively small anharmonic effects.","hedge":{"p":0.7,"label":"hedged_possibility"},"own_p":0.92,"main_claim_p":0.04,"quantitative":false,"quantitative_p":0.23,"role_probabilities":{"gap":0.0,"method":0.18,"result":0.79,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.03,"interpretation":0.0}},{"i":6,"p":0.82,"id":"s6","own":true,"role":"result","text":"Despite their high $T_\\mathrm{c}$, both phases contain elongated H$_2$-like units, often considered unfavorable for high-$T_\\mathrm{c}$ hydrides.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.7,"main_claim_p":0.09,"quantitative":false,"quantitative_p":0.1,"role_probabilities":{"gap":0.02,"method":0.0,"result":0.82,"background":0.01,"limitation":0.05,"future_work":0.0,"contribution":0.01,"interpretation":0.09}},{"i":7,"p":0.67,"id":"s7","own":true,"role":"result","text":"Mode-resolved electron-phonon coupling links Raman-active hydrogen vibrations to superconductivity.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.84,"main_claim_p":0.05,"quantitative":false,"quantitative_p":0.03,"role_probabilities":{"gap":0.0,"method":0.17,"result":0.67,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.1,"interpretation":0.06}},{"i":8,"p":0.89,"id":"s8","own":true,"role":"result","text":"In $R\\bar{3}m$, the linewidths of these modes increase with the pressure-induced tilt of H$_2$ units relative to the threefold axis, alongside the rise in $T_\\mathrm{c}$.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.89,"main_claim_p":0.07,"quantitative":false,"quantitative_p":0.21,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.89,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.11}},{"i":9,"p":0.75,"id":"s9","own":true,"role":"interpretation","text":"A minimal symmetry-based model of the vibration-induced second-moment tensor of the hydrogen sublattice shows that these trends are consistent with a significant contribution from response components perpendicular to the threefold axis.","hedge":{"p":0.95,"label":"hedged_possibility"},"own_p":0.88,"main_claim_p":0.09,"quantitative":false,"quantitative_p":0.12,"role_probabilities":{"gap":0.0,"method":0.13,"result":0.08,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.04,"interpretation":0.75}},{"i":10,"p":1.0,"id":"s10","own":true,"role":"interpretation","text":"NaH$_6$ thus represents an unusual molecular-like hydride in which hydrogen-sublattice reorganization may enable high-$T_\\mathrm{c}$ superconductivity at comparatively moderate pressures.","hedge":{"p":0.83,"label":"hedged_possibility"},"own_p":0.82,"main_claim_p":0.87,"quantitative":false,"quantitative_p":0.28,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":1.0}}]},"compiled":{"main_claim":{"p":1.0,"text":"NaH$_6$ thus represents an unusual 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