Frozen density embedding with non-integer subsystems' particle numbers
  We extend the frozen density embedding theory to non-integer subsystems' particles numbers. Different features of this formulation are discussed, with special concern for approximate embedding calculations. In particular, we highlight the relation between the non-integer particle-number partition scheme and the resulting embedding errors. Finally, we provide a discussion of the implications of the present theory for the derivative discontinuity issue and the calculation of chemical reactivity descriptors. 
E. Fabiano, S. Laricchia, F. Della Sala
physics.chem-ph cond-mat.other