  The study of hard-particle packings is of fundamental importance in physics,
chemistry, cell biology, and discrete geometry. Much of the previous work on
hard-particle packings concerns their densest possible arrangements. By
contrast, we examine kinetic effects inevitably present in both numerical and
experimental packing protocols. Specifically, we determine how changing the
compression/shear rate of a two-dimensional packing of noncircular particles
causes it to deviate from its densest possible configuration, which is always
periodic. The adaptive shrinking cell (ASC) optimization scheme maximizes the
packing fraction of a hard-particle packing by first applying random
translations and rotations to the particles and then isotropically compressing
and shearing the simulation box repeatedly until a possibly jammed state is
reached. We use a stochastic implementation of the ASC optimization scheme to
mimic different effective time scales by varying the number of particle moves
between compressions/shears. We generate dense, effectively jammed,
monodisperse, two-dimensional packings of obtuse scalene triangle, rhombus,
curved triangle, lens, and "ice cream cone" (a semicircle grafted onto an
isosceles triangle) shaped particles, with a wide range of packing fractions
and degrees of order. To quantify these kinetic effects, we introduce the
kinetic frustration index $K$, which measures the deviation of a packing from
its maximum possible packing fraction. To investigate how kinetics affect
short- and long-range ordering in these packings, we compute their spectral
densities and characterize their contact networks. We find that kinetic effects
are most significant when the particles have greater asphericity, less
curvature, and less rotational symmetry. This work may be relevant to the
design of laboratory packing protocols.
