Cooperative Atomic Motion in the Interfacial Dynamics of Strongly Interacting Particle Systems

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Thermally excited collective string-like particle motion is a general property of strongly interacting particle systems. It has recently become noticed that this type of cooperative motion is characteristic of the dynamics of diverse forms of glass forming liquids. Such collective atomic motion has been found in recent molecular dynamics simulations in the bulk dynamics of a wide range of glass forming liquids, and it has been directly observed in measurements on colloidal 'hard sphere' fluids. The applicant's previous molecular dynamics simulations have further indicated that string-like collective motion is prevalent in grain boundaries of polycrystalline materials and interface of nanoparticles. The recognition of the these general thermal excitations provides a general framework for understanding the sensitivity of strongly interacting particle systems to impurities, pressure and geometrical confinement and other factors that affect atomic packing and the scale of collective atomic motion. The new perspective of the origin of the special and tunable properties of strongly interacting particle systems also offers the promise of an improved rational control of their properties based on further quantification and manipulation of their interfacial chemistry and environment. The objectives of current proposal are to 1) taking nickel nanoparticles and ice-water as strongly interacting particle model systems, investigate and characterize cooperative atomic motion during sintering of nickel nanoparticles and premelting of ice, and 2) using various types of perturbations (e.g., molecular and alloy additives, hydrostatic pressure, nanoconfinement), modify the cooperative atomic motion and better understand how such collective motions influence dynamics of sintering and premelting with goals to prevent sintering and to control premelting of ice.