Interface Confinement and Electric Field Synergy Orchestrate "Ångström-Scale Chain Forest" of Undercoordinated Water: Orientation Control and Non-Monotonic Thermodynamic Response

Nanowires and Ångström-scale wires represent quintessential one-dimensional material systems, bridging the mesoscopic and atomic scales to underpin functional device engineering and cutting-edge quantum technologies. This study investigates the self-assembly of undercoordinated water molecules orchestrated by the synergistic interplay of interfacial confinement and an external electric field. Through integrated molecular dynamics simulations (COMPASSII force field, NVT ensemble) and first-principles calculations, we unveil a novel quasi-one-dimensional architecture: a highly ordered "forest" of vertically aligned water molecule chains at the Ångström scale. Key findings reveal that under conditions of low water density and narrow interfacial spacing, the synergistic application of an electric field directs self-assembly into these vertical chain arrays, endowing water molecules with enhanced orientational freedom compared to bulk ice. Strikingly distinct stability regimes emerge upon field removal: the chain structure persists as a kinetically arrested metastable state at cryogenic temperatures (1-100 K), while relaxation into a two-dimensional film occurs at near-ambient and ambient temperatures (200-300 K). The system's total energy landscape is governed by a delicate interplay of competing contributions―orientational energy, hydrogen-bond reconfiguration, adsorption energy, and electric field storage―manifesting a pronounced non-monotonic thermodynamic response. Stability and structural evolution are collectively modulated by electric field strength, temperature, water density, interfacial spacing, and substrate material properties. The proposed strategy of "interfacial confinement + electric field + thermal control" establishes a theoretical pathway for the scalable fabrication of one-dimensional Ångström chains. This multiphysics framework provides fundamental theoretical insights for the design and application of complex interfacial-electric field-water systems, opening avenues in nanofluidics, molecular sensing, energy storage and conversion, and next-generation nanodevices.