MOLPRO

31 EXPLICITLY CORRELATED METHODS 228
default,vdz/jkfit }
hf
{lt-df-lcc2
!ground state CC2
!five lowest triplet states, dipole moments for four lowest, density saved:
eom,-6.1,triplet=1,singlet=0,propes=-5.1,densave=5000.2
eomprint,popul=-1,loceom=-1 } !minimize the output
!ground state density, file h2o0_density.cube:
{cube,h2o0,,80,80,80
density,5000.2,cc2 }
!difference excited state density, file h2o1_density.cube:
{cube,h2o1,,80,80,80
density,5000.2,diff,state=2.1 }
31 EXPLICITLY CORRELATED METHODS
Explicitly correlated calculations provide a dramatic improvement of the basis set convergence
of MP2 and CCSD correlation energies. Such calculations can be performed using the commands
of the form
command, options
where command can be one of the following:
MP2-F12 Closed-shell canonical MP2-F12. By default, the fixed amplitude
ansatz (FIX, see below) is used, but other ansätze are also possible.
The F12-corrections is computed using density fitting, and then added
to the MP2 correlation energy obtained without density fitting.
DF-MP2-F12
DF-LMP2-F12
DF-RMP2-F12
CCSD-F12
CCSD-F12c
CCSD(T)-F12
As MP2-F12, but the DF-MP2 correlation energy is used. This is less
expensive than MP2-F12.
Closed-shell DF-MP2-F12 with localized orbitals. Any method and
ansatz as described in J. Chem. Phys. 126, 164102 (2007) can be used
(cf. secions 31.2,31.7).
Spin-restricted open-shell DF-RMP2-F12 using ansatz 3C. Any method
as described in J. Chem. Phys. 128, 154103 (2008) can be used (cf.
sections 31.2,31.7).
Closed-shell CCSD-F12 approximations as described in J. Chem. Phys.
127, 221106 (2007). By default, the fixed amplitude ansatz is used
and the CCSD-F12A and CCSD-F12B energies are computed. Optionally,
the command can be appended by A or B, and then only
the corresponding energy is computed. For more details see section
31.10.
Closed-shell CCSD(F12*) approximation as proposed by Hättig, Tew
and Köhn. In Molpro this is denoted f12c. As compared to CCSD-
F12a/b it requires additional computational effort. Since in some parts
the implementation is brute-force without paging algorithms, large
memory may be required. In most cases there is no gain in accuracy
as compared to f12b and therefore the use of this method is normally
not recommended. Currently CCSD-F12c is not available for openshell
cases.
Same as CCSD-F12, but perturbative triples are added.