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Physics Chemistry

6
Open Unknowns
0
Cross-Domain Bridges
6
Active Hypotheses

Open Unknowns (6)

Unknown Whether the Arrhenius pre-exponential factor A can be predicted from first principles for arbitrary reactions, and to what degree A encodes steric, entropic, and quantum tunnelling contributions distinguishable from experiment alone u-arrhenius-prefactor-molecular-basis
Unknown Can the crystallographic phase problem be solved ab initio for large macromolecules (>100 kDa) using only measured intensities |F_{hkl}|², without experimental phasing or molecular replacement, through computational approaches combining direct methods, charge flipping, and machine learning? u-crystallography-phase-problem-ab-initio
Unknown What are the exact constraints that the exchange-correlation functional E_xc[rho] must satisfy, and can a functional satisfying all known exact constraints (non-empirical, fully ab initio) achieve chemical accuracy for arbitrary molecular and materials systems? u-dft-exchange-correlation-exact-functional
Unknown What is the electron pairing mechanism in cuprate and iron-based high-temperature superconductors — phonon, spin-fluctuation, charge-density-wave, or something else entirely? u-high-tc-superconductor-pairing-mechanism
Unknown What are the dominant atomic-scale degradation mechanisms of Pt/C oxygen reduction catalysts in PEM fuel cells under drive-cycle conditions — and can they be suppressed to achieve 150,000-hour durability targets for heavy-duty transportation? u-pem-fuel-cell-pt-catalyst-degradation-mechanism
Unknown What is the topological mechanism of polymer entanglement, and can entanglement constraints be derived from first principles without the tube model assumption? u-polymer-entanglement-topology

Active Hypotheses

Hypothesis The Arrhenius equation is a universal consequence of the Maxwell-Boltzmann tail integral for any thermally activated process, and deviations from Arrhenius behaviour (curved Arrhenius plots) are diagnostic for quantum tunnelling, multi-step mechanisms, or temperature-dependent activation energy medium
Hypothesis For membrane proteins with molecular weight >200 kDa, cryo-EM single-particle analysis now routinely achieves higher resolution than X-ray crystallography for native-like structural states — making crystallography obsolete for this protein class while remaining superior for small, rigid proteins where cryo-EM faces orientational sampling limitations. medium
Hypothesis Antiferromagnetic spin fluctuations are the dominant Cooper pairing glue in cuprate high-temperature superconductors, predicting d-wave symmetry order parameter and T_c proportional to the superexchange coupling J. high
Hypothesis The Jacob's Ladder of DFT approximations (LDA → GGA → meta-GGA → hybrid → double hybrid) systematically approaches chemical accuracy by satisfying increasingly many exact constraints, with each rung reducing mean absolute error in thermochemistry by ~50%; hybrid functionals already achieve near-chemical-accuracy for organic molecules and the remaining gap arises specifically from strong- correlation systems and delocalization error. high
Hypothesis The discrepancy between predicted (η ∝ N³) and observed (η ∝ N^3.4) viscosity exponents in entangled polymer melts is fully accounted for by contour-length fluctuations and constraint release acting together, and the combined model prediction converges to ν=3.4 in the experimentally accessible molecular weight range before asymptotically returning to ν=3 at N >> N_e. medium
Hypothesis Single-atom catalysts (SACs) with atomically dispersed Fe–N₄ sites on carbon achieve near-100% selectivity for the 4-electron oxygen reduction reaction pathway (O₂ → H₂O) over the 2-electron pathway (O₂ → H₂O₂) because the Fe coordination geometry enforces the correct O–O bond activation angle, making SACs viable Pt-free ORR catalysts for commercial PEM fuel cells. high

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