A solution of the gauge origin problem for the magnetic susceptibility

A polarization propagator based theory for calculation of the diamagnetic part of the magnetic susceptibility is presented. Since the paramagnetic term also may be obtained from the propagator it is thus possible to compute both contributions at the same level of approximation, e.g., in RPA, SOPPA, and CCPPA. Contrary to other commonly used procedures the present method gives a total result for the susceptibility, which—even in a limited basis set—is independent of the origin chosen for the vector potential.