HARTREE ENERGY
Definition
A <HARTREE ENERGY> is an <ENERGY> that is is a physical constant equal to twice the binding energy of the electron in the ground state (the lowest-energy state) of the hydrogen atom . When a hydrogen atom is in this state, an amount of energy equal to 0.5 Hartree is necessary to free the electron and thereby cause the atom to become an ion . It is calculated as E_H = e^2/(4.pi.epsilon_0.a_0) where e is an <ELEMENTARY CHARGE>, epsilon_0 is the electric constant, and a_0 is A <BOHR RADIUS>