  We examine the impact of the intrinsic molecular reorganization energy on
switching in two-state quantum-dot cellular automata (QCA) cells. Switching a
bit involves an electron transferring between charge centers within the
molecule. This in turn causes the other atoms in the molecule to rearrange
their positions in response. We capture this in a model that treats the
electron motion quantum-mechanically, but the motion of nuclei semiclassically.
This results in a non-linear Hamiltonian for the electron system. Interaction
with a thermal environment is included by solving the Lindblad equation for the
time-dependent density matrix. The calculated response of a molecule to the
local electric field shows hysteresis during switching when the sweep direction
is reversed. The relaxation of neighboring nuclei increases localization of the
electron, which provides an intrinsic source of enhanced bistability and
single-molecule memory. This comes at the cost of increased power dissipation.
