Beginning at the Born-Oppenheimer adiabatic approximation , whereby it is assumed that the nuclear mass is much larger than that of the electrons that therefore the velocity is much faster than that of the nuclei, the total Hamiltonian can be expressed in terms of operators for the electronic kinetic energy T (q) and nuclear kinetic energy T (q), and the total electronic potential energy U (q, Q) and potential energy of the nuclei L (Q) :