Spin-adapted Matrix Product States and Operators
  Matrix product states (MPSs) and matrix product operators (MPOs) allow an alternative formulation of the density matrix renormalization group algorithm introduced by White. Here, we describe how non-abelian spin symmetry can be exploited in MPSs and MPOs by virtue of the Wigner--Eckart theorem at the example of the spin-adapted quantum chemical Hamiltonian operator. 
Sebastian Keller and Markus Reiher
physics.chem-ph cond-mat.str-el physics.comp-ph