The molecules at the surface of a liquid have different organization and dynamics from those in the bulk, potentially altering the rate of crystal nucleation and polymorphic selection, but this effect remains poorly understood. Here we demonstrate that nucleation at the surface of a pure liquid, d-arabitol, is vastly enhanced, by 12 orders of magnitude, and selects a different polymorph. The surface effect intensifies with cooling and can be inhibited by a dilute, surface-active second component. This phenomenon arises from the anisotropic molecular packing at the interface and its similarity to the surface-nucleating polymorph. Our finding is relevant for controlling the crystallization and polymorphism in any system with a significant interface such as nanodroplets and atmospheric water.

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Hydrogenous species play critical roles in the synthesis and catalysis applications of mayenite electride. In this work, we investigate their formation energetics and transport mechanisms in mayenite using ab initio simulations. The chemical potentials of various hydrogenous species are established based on static density functional theory calculations. Clathrated H − and OH − are identified to be energetically favored products following mayenite's reaction with hydrogen gas. Clathrated H 0 , which was observed experimentally under UV irradiation, is unstable under normal conditions and has a strong thermodynamic tendency to react with electrons or clathrated O 2− . The transport mechanisms of clathrated H − , OH − , and H 0 are studied with first-principles nudged elastic band calculations. H − hops between nanocages through intercage openings with an energy barrier of 1.24 eV. OH − transport resembles the diffusion of clathrated O 2− , i.e., through exchanges with framework O 2− . This process has an energy barrier of 1.67 eV, lower than that for OH − dissociation, suggesting H + /OH − conduction mediated by oxygen transport is an energetically preferred mechanism over direct proton hopping. On the basis of the energetics and kinetics data of these hydrogenous species, we evaluate the rate-limiting steps in the electride synthesis approach via the H 2 treatment followed by UV irradiation. Under a typical experimental condition of 1300 °C and P H 2 = 0.2 atm, only ∼2% of the clathrated oxygens will react with H 2 at equilibrium to form H − and OH − . In the subsequent UV irradiation step, the short lifetime of H 0 and the availability of clathrated O 2− in the vicinity of H − are the likely limiting factors. Also, we report that the electron concentration generated from this approach will decay at high temperatures with an energy barrier predicted to be around 0.7−1.0 eV.

As one of the most common minerals composing felsic to intermediate rocks, phyllosilicate minerals oftentimes hold an important control on the mechanical behavior of rocks. Due to their sheet structure, morphology, and the porous aggregate they form in sedimentary rocks, phyllosilicate minerals, including clays, micas, chlorites, and serpentine groups, are known to cause anisotropy in the bulk rock properties and

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