BEGIN_PROVIDER [ double precision, taus, (spin_occ_num,spin_occ_num,spin_vir_num,spin_vir_num)]
 implicit none
 BEGIN_DOC
 ! Tau_s
 END_DOC

  integer                       :: i,j,a,b

  do b=1,spin_vir_num
   do a=1,spin_vir_num
    do j=1,spin_occ_num
     do i=1,spin_occ_num

          taus(i,j,a,b) = t2_cc(i,j,a,b) + 0.5d0*(                   &
              t1_cc(i,a)*t1_cc(j,b) -                                &
              t1_cc(i,b)*t1_cc(j,a) )

        enddo
      enddo
    enddo
  enddo

END_PROVIDER