  Intuition tells us that a rolling or spinning sphere will eventually stop due
to the presence of friction and other dissipative interactions. The resistance
to rolling and spinning/twisting torque that stops a sphere also changes the
microstructure of a granular packing of frictional spheres by increasing the
number of constraints on the degrees of freedom of motion. We perform discrete
element modeling simulations to construct sphere packings implementing a range
of frictional constraints under a pressure-controlled protocol. Mechanically
stable packings are achievable at volume fractions and average coordination
numbers as low as 0.53 and 2.5, respectively, when the particles experience
high resistance to sliding, rolling and twisting. Only when the particle model
includes rolling and twisting friction, were experimental volume fractions
reproduced.
