Figure 4: Typical localized grain-boundary structures under mechanical loading.
From: Mechanical instability of monocrystalline and polycrystalline methane hydrates
Localized grain-boundary snapshots of polycrystalline methane hydrates with grain sizes of (a) 5.61 nm and (b) 28.1 nm at the initial, maximum stress and maximum preset strain stages under tension. Localized grain-boundary snapshots of polycrystals with grain sizes of (c) 5.61 nm and (d) 28.1 nm at strains of 0.0, 0.06 and 0.15 under compression. The snapshots of numbers 1–3 are coloured according to the molecular von Mises stresses, whereas the snapshots of numbers 4–6 are coloured according to their cage-type formation. (e) Zoomed-in molecular structures of polycrystals with a grain size of 28.1 nm at strains of 0.0 and 0.15, as framed in d4 and d6. Water particles are coloured with either aqua or black in a–d for monitoring grain-boundary sliding. Water particles are coloured with either blue or orange near the grain boundary in e for identifying the structural transformations upon pressurization.
