The geometry of PFOA/PFOS + 43 H2O molecules in a 29×24×22 Å 3 simulation box was first optimized such that the residual forces were less than 0.01 eV/Å (a large box size was chosen to prevent periodic images of the system from interacting with each other). This optimized geometry was then used as an initial condition for the excited-state, photo-induced Ehrenfest dynamics, and the resulting atomic positions were monitored at each time step. We used an optical pulse with ω set to either 6 or 7.5 eV with a ~10 W/cm 2 intensity, which is commensurate with field strengths used in photocatalysis experiments. Our simulations were carried out for a total of 36 fs with a timestep of 10 attoseconds (the electromagnetic optical pulse (c.f. Figure ) acts on the system for the first 20 fs). Finally, it is worth noting that these excited-state RT-TDDFT calculations are significantly more expensive than conventional ground-state DFT calculations, and this work utilized a total of over 570,000 CPU hours on the XSEDE Comet computing cluster.