Water Freezing as Donor–Acceptor Boundary Locking in USP Field Theory

msf:52712 v2.0.1 presents an experimentally constrained multiscale framework for water freezing from molecular polarity and hydrogen-bond dynamics to supercooled-liquid structure, stochastic nucleation, crystalline ice Ih, and atmospheric mixed-phase handoff. The document retains the USP donor–acceptor boundary interpretation while preserving standard quantum chemistry, thermodynamics, spectroscopy, nucleation theory, scattering, molecular simulation, and crystallography as the quantitative baseline. Water’s bent polar geometry provides two hydrogen-bond donor directions and two acceptor directions. USP translates this into directional donor and acceptor boundary corridors, but this language does not replace electrostatics or conventional hydrogen-bond physics. The earlier idea of one universal freezing-frequency threshold is retired. In particular, the condition σ_Δf < σ_crit is not treated as a physical freezing law. Experiments show that water contains multiple dynamical channels with distinct timescales: ultrafast OH vibration and coherence, spectral and structural memory, dielectric relaxation, orientational reorientation, hydrogen-bond exchange, intermediate-range O–O structural organization, nucleation, crystal emergence, and later crystal growth. These processes cannot be collapsed into one universal relaxation time or one monotonic fluctuation variable. Version 2.0.1 therefore builds a multichannel water-state description from experimentally measurable quantities. The observable block includes quantities such as: structural correlation time, orientational relaxation, dielectric response, O–O pair structure, and structural/network order. External controls are kept separately, including: temperature, pressure, droplet size, cooling rate, interfaces, solute or ice-nucleating-particle state, and preparation history. A low-dimensional USP representation may then be written schematically as: κ_lock = G(Q_water; φ). κ_lock is a Level-C representation. It is not a new thermodynamic state variable by assumption. If it is constructed only from conventional observables already supplied to the baseline model, it contains no additional physical information. The primary transition targets are therefore independently measurable quantities such as: J_hom homogeneous nucleation rate, P_freeze freezing probability, phase fraction, Raman or x-ray phase observables, and crystal-emergence time. The conventional survival relation remains primary: S(t) = exp[-∫ J_hom(T(t′),...) V(t′) dt′], with: P_freeze(t) = 1 − S(t). USP does not replace nucleation theory. A genuine USP extension requires predictive information beyond the matched conventional baseline. The exact additional-physics null remains: A_USP = 0. No nonzero Level-D USP residual is claimed. The ice-Ih endpoint is treated through established experimental constraints. Neutron diffraction owns lattice and proton geometry. Density measurements preserve the open-lattice consequence of ice being less dense than liquid water. Preparation-dependent polarization observed in specially grown crystalline ice films is retained as an experimental endpoint, but is not extrapolated to bulk liquid-frozen ice, atmospheric crystals, or cloud electrification. The atmospheric handoff is deliberately limited. msf:52712 may export quantities such as: J_hom, P_freeze, f_ice, f_SLW, ice number, liquid-water content, ice-water content, and phase diagnostics. It does not generate atmospheric charge, electric fields, or lightning. Those processes remain downstream in msf:49910. The central v2.0.1 rule is therefore: water freezing may be described in USP language as increasing donor–acceptor network persistence culminating in crystalline locking, but the representation earns physical meaning only if it predicts independent freezing or phase observables beyond a matched standard baseline. *SHORT ZENODO SUMMARY A multiscale experimental framework for water freezing from molecular polarity and hydrogen-bond dynamics through supercooled structure, stochastic nucleation, and ice Ih. USP donor–acceptor locking is retained only as a calibrated representation, with J_hom, P_freeze, and phase observables as independent targets under the exact null A_USP = 0. Atmospheric export is limited to probabilistic phase-state quantities; cloud electrification and lightning remain downstream.