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In this paper, we report an in situ optical microscopy study of lateral growth of xenon (Xe) hydrate thin films on mica at sub-zero temperatures. The interactions between a solid surface and water molecules can strongly affect the alignment of water molecules and induce ice-like ordered structures within the water layer at the water-surface interface. Mica was chosen as a model surface to study the surface effect of hydrophilic sheet silicates on the lateral growth of Xe hydrate films. Under the experimental conditions, the lateral growth of Xe hydrate films was measured to be at an average rapid rate of ~200 µm/s and 400 µm/s under two different pressures of Xe. Mass transfer estimation of the Xe-water system revealed that the increasing trend of lateral film growth rates followed the increase in the net mass flux and aqueous solubility of Xe. However, as the supercooling temperature increased, the trend of lateral film growth rates attained a plateau region where little change in the rate was observed. This unique feature in the lateral film growth trend, the fast lateral growth kinetics, and the short induction time for hydrate film growth hinted at the assistance of the mica surface to aid the lateral growth process of Xe hydrate films at low Xe mass flux and at a low degree of subcooling. A mechanism based on the reported structured water layer at the interface on mica was proposed to rationalize a postulated surface-promotional effect of mica on the nucleation and lateral growth kinetics of Xe hydrate films. [ABSTRACT FROM AUTHOR]

In this study, we report our efforts to elucidate the electronic structures of two lattice structures of lanthanide sulfides (LnS and Ln3S4) and for three lanthanides (Ln = La, Sm and Gd) using density functional theory calculations performed with the CASTEP code. A DFT+U method was used for the corrections of on-site Coulomb interactions with U = 6 eV. The calculated electronic structures show that both lanthanum and gadolinium sulfides have metallic properties, consistent with the available experimental results. However, the calculated electronic structure of Sm3S4 is considerably different from those of the La3S4 and Gd3S4 and is predicted to have semiconducting properties. [ABSTRACT FROM AUTHOR]