We tested the convergence of the CSS-AIMS method with respect to the number of initial conditions. We found that after five initial conditions, the population trace converged (see Figure of section 4 in the SI). Note that the norms for all CSS-AIMS runs (but one) deviate from unity by no more than 0.01. The only simulation that crossed this norm-conservation threshold was disregarded for calculating expectation values (see Figure of section 4 in the SI for the details on norm conservation). As expected, the total energy expectation value is not entirely conserved since the basis sets used in the individual CSS-AIMS simulations are far from complete. However, the maximum deviation in the total energy is very low, around 0.04 eV (see Figure of section 4 in the SI).