A partial differential equation for pseudocontact shift
  It is demonstrated that pseudocontact shift (PCS), viewed as a scalar or a tensor field in three dimensions, obeys an elliptic partial differential equation with a source term that depends on the Hessian of the unpaired electron probability density. The equation enables straightforward PCS prediction as well as analysis of experimental PCS data in systems with multiple and / or distributed unpaired electron centres. 
G.T.P. Charnock, Ilya Kuprov
physics.chem-ph physics.bio-ph