and μ1 and μ2 are, respectively, the sets
of all singly and doubly excited determinants.
Eq. (10.5) is computational much more complex and
demanding than the corresponding doubles equations for the CC2 model.
If is a measure for the system size
(e.g. the number of atoms), the computational costs
(in terms of floating point operations) for CCSD
calculations scale as
If for the same molecule the number of one-electron basis functions
N is increased the costs scale with
(For RI-MP2 and RI-CC2 the costs scale with the system size
(5) and with the number of basis functions