As a new example of spontaneous pattern formation in many-body systems,
we examine the collective means by which a close-packed disk crystal reacts to
the presence of a single oversized impurity disk. Computer simulation has been
used for this purpose; it creates the jammed impurity-containing packings by a
kinetic particle-growth algorithm. Hexagonal primitive cells with periodic
boundary conditions were employed, and the "natural" number 3n 2 of disks
(including the impurity) ranged up to 10,800. For impurity diameter 1.2 times
that of the other disks, the patterns of observed crystal perturbation displayed
several remarkable features. Particle displacements relative to the unperturbed
triangular crystal possess local irregularity but long-range coherence.