Hence, the PCM-induced density change is expected to be pronounced for highly polarizable molecules, such as highly conjugated molecules. For example, the all-trans retinoic acid anion is a highly conjugated molecule widely studied for its importance in photochemistry. Its Δ𝐸 Z &%' reaches 0.096 eV at ε=2.0 and further increases to 0.500 eV at ε=80.0. This energy difference indicates a non-trivial density difference between the CPCM converged wave function and the gas-phase ground state wave function (Table ). The isosurface plot of 𝑛 &%' -𝑛 XYL (Figure ) also shows a significant difference in the electron densities on the conjugated π bonds obtained from the gas phase vs CPCM. It is worth mentioning that CPCM does not accelerate the SCF convergence of this molecule because it has a non-zero HOMO-LUMO gap. This example demonstrates the limitation of CPCM as an SCF convergence technique.