A brick is a compacted, bonded assembly that may be replicated many times to construct a large model. The brick is derived (in a separate PFC run) by compacting an assembly of particles within periodic space and then storing it in compact form. Copies of this assembly can then be fitted together perfectly, because the geometrical arrangement of particles on one side of a brick is the negative image of that on the opposite side (see image below).


A large model may be constructed very quickly because the bricks are already compacted and in equilibrium. (Note that contact forces are also stored within the brick, and these automatically balance at the junction between two bricks if the original forces were in equilibrium.) Typically, the time necessary to bring a model to equilibrium increases greatly with the size of the model, because information (about unbalanced forces) must be transmitted repeatedly across the entire model. When a model is constructed of already equilibrated bricks, no further time is necessary to establish global equilibrium. Thus, a large equilibrated model may be assembled almost instantaneously.