The additional hardness parameters ∆η included in the J matrix are rather small, and so the energetic cost to move charge to or from a site is still mostly due to it's electrostatic self interaction. Additionally, as AmberFD only allows for another fragment's nuclei and frozen densities to be the cause for polarization, the energy to polarize a nucleobase is primarily driven by Coulombic forces in origin. As such, the combination of E pol , E ct (which is a fraction of E pol ), and E elec together comprise a version of induction that is mostly classical and driven by Coulomb's law.