Supersonic motion of vacancies in a polyethylene crystal - art. no. 036702

The possibility of supersonic motion of vacancies in a polyethylene crystal is revealed by means of analytical investigation and numerical simulation. It is demonstrated that in the crystalline field of immovable neighbors, a vacancy with a core size of about 70 CH2 groups and a velocity in the rang e of 1.02-1.05 sound velocity preserves itself for the time scale of about 1 ns. It is demonstrated that this type of structural defect is similar to coupled supersonic solitons described earlier in the one-dimensional chains with combined gradient and nongradient nonlinearity. An analytic approach is proposed for prediction of their shape and velocity. The simulation of t he crystal with all degrees of freedom released demonstrates that the super sonic vacancy is still distinguishable, Its lifetime is less than 5 ps but still may be significant for physical applications.