The role of non-hydrostatic stresses in phase transitions in boron carbide

The structural changes in boron carbide B4C under non-hydrostatic stresses were studied by quantum molecular dynamics simulation. Three different structural changes were observed: abrupt and continuous bending of three-atomic chain and the disordering of the structure. The differences between them are discussed in terms of crystal symmetry. The existence of special deformation direction could activate abrupt bending above 40 GPa, while at quasi-hydrostatic loading structure remains stable up to 70 GPa. Crystal defects can reduce threshold value of stress therefore explain possible structural transitions observed in some experiments.

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