Activated solids: Spontaneous deformations, non-affine fluctuations, softening, and failure

Abstract: We investigate spontaneous deformations in activated solids by analyzing crystal deformations through non-affine fluctuations. A scaling law for non-affinity is derived, showing it scales quadratically with activity and inversely with density. At high activity, the non-affine parameter diverges, signaling defect proliferation and melting to a hexatic phase. This softening is marked by reduced shear modulus, solid order, and hexatic order. At a higher activity, the hexatic melts to a fluid. We propose locally tuned activity to control non-affinity, demonstrated through numerical simulations. Our predictions are testable in active colloids performing persistent random motion.