  Singlet fission, which has applications in areas ranging form solar energy to
quantum information, relies critically on transitions within a multi-spin
manifold. These transitions are driven by fluctuations in the spin-spin
exchange interaction, which have been linked to changes in nuclear geometry or
exciton migration. Whilst simple calculations have supported this mechanism, to
date little effort has been made to model realistic fluctuations which are
informed by the actual structure and properties of physical materials. In this
paper, we develop a modular computational pipeline for calculating singlet
fission spin dynamics by way of electronic structural calculations, molecular
dynamics, and numerical models of spin dynamics. The outputs of this pipeline
aid in the interpretation of measured spin dynamics and allow us to place
constraints on geometric fluctuations which are consistent with these
observations.
