To verify our implementation within PySCES with the TeraChem interface, we compared the dynamics of ethylene using (2,2) SA-CASSCF with both GAMESS and TeraChem drivers. An initial nuclear geometry was generated from a Wigner distribution over normal mode coordinates and frequencies determined from a ground state CAM-B3LYP/6-31G(d) computation. Classical electronic variables were also randomly assigned an angle in x, p phase space according the the Wigner distribution in Eq. 11. The S 0 , S 1 , and S 2 states were used in this assignment with an initial photoexcitation to S 1 . Both trajectories with GAMESS and TeraChem used the exact same initial conditions for each trajectory. FIG. . Energy and occupations of the S0, S1, and S2 states of ethylene for a single LSC trajectory with identical initial conditions generated by PySCES. Deviation between GAMESS and TeraChem due to a build up of small numerical differences becomes apparent after 35 fs.