This paper discusses the mechanical effect of water on the deformation of silicon monocrystals under nano-indentation with the aid of molecular dynamics analysis. The rigid TIP4P model was used to simulate the interactions between water molecules while the long-ranged non-bonded Lennard-Jones potential was applied for the pairs of unlike molecules. It was found that upon loading water molecules are lodged into the cavities of the silicon substrate, causing subsurface damage. The diamond cubic structure in the indentation zone transforms into an amorphous state with a body-centred tetragonal form (β-silicon) below the indentor. The presence of water significantly reduces the indentor-silicon adhesion that alters the structure of the residual deformation zone after complete unloading.
The backward cross section of hexagonal ice crystals of arbitrary orientation is calculated for visible light by means of a ray-tracing code. It is shown that backscattering of the tilted crystals is caused by a corner-reflector-like effect. A very large peak of backscattering is found for a tilt of 32.5 degrees between the principal particle axis and the incidence direction. This peak is caused by multiple total internal reflections for part of the rays that are incident upon the skewed rectangular faces. Slant lidar measurements for remote sensing of cirrus clouds are proposed.
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