Answer

An ab initio (from first principles) model predicts the behavior of a system using only fundamental laws and universal constants, without empirical data or pre-existing adjustments. It is quantum because it solves for the interaction of electrons based on the Schrödinger equation and physical constants; it is classical mechanics because it derives the dynamics of bodies solely from Newton’s laws or the principle of least action; and so is classical electromagnetism, whose axiomatic first principles are the four Maxwell equations along with the Lorentz force and the conservation of charge.