Next: Required input data:
Up: CC2 Ground-State Energy Calculations
Previous: CC2 Ground-State Energy Calculations
For RI-CC2 calculations,
the operation count and thereby the
CPU and the wall time increases--as for RI-MP2 calculations--approximately
, where is the
number of occupied and the number of virtual orbitals
and the dimension of the auxiliary basis set for
the resolution of the identity.
Since RI-CC2 calculations
require the (iterative) solution of the cluster
equations (9.5) and (9.6), they are about 10-20 times more
expensive than MP2 calculations.
The disk space requirements are approximately
double precision words.
The details of the algorithms are described in ref. , for
the error introduced by the RI approximation see