  We develop a computational method for modeling electrostatic interactions of
arbitrarily-shaped, polarizable objects on colloidal length scales, including
colloids/nanoparticles, polymers, and surfactants, dispersed in explicit ion
electrolytes and nonionic solvents. Our method computes the nonuniform
polarization charge distribution induced in a colloidal particle by both
externally applied electric fields and local electric fields arising from other
charged objects in the dispersion. This leads to expressions for electrostatic
energies, forces, and torques that enable efficient molecular dynamics and
Brownian dynamics simulations of colloidal dispersions in electrolytes, which
can be harnessed to accurately predict structural and transport properties. We
describe an implementation in which colloidal particles are modeled as rigid
composites of small spherical beads that tessellate the surface of the
particle. The electrostatics calculations are accelerated using a
spectrally-accurate particle-mesh-Ewald technique implemented on a graphics
processing unit (GPU) and regularized such that the electrostatic calculations
are well-defined even for overlapping bodies. We demonstrate the effectiveness
of this approach through a series of calculations, including the induced dipole
moments and forces for one, two, and lattices of spherical colloids in an
electric field; the induced dipole moment and torque for anisotropic particles
in an electric field; the equilibrium distribution of ions in the double layer
around charged colloids; the dynamics of charged colloids; and ions in the
double layer around a polarizable colloid exposed to an electric field.
