Through molecular dynamics, the characteristics of crack propagation on basal and prismatic planes in single-crystal ice Ih were investigated as functions of temperature and salinity at the atomic scale. The fracture toughness was found to increase with decreasing temperature. At low temperatures, cracks propagated in a brittle manner along cleavage planes due to the sequential breaking of the hydrogen bonds under the most stress directly in front of the sharp crack tip. Amorphization occurred at the crack tip above 125 K. However, the brittle-ductile transition (BDT) did not change the brittle fracture characteristics of the ice. The crack underwent BDTs at both low and high temperatures due to the interactions between the salt and water molecules at the tip. This transition contributed to a gradual increase in fracture toughness with increasing salinity but did not change the ultimate brittle fracture properties of the ice.
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