MOLPRO

30 LOCAL METHODS FOR EXCITED STATES 224
BASIS MP2=string
BASIS CCSD=string
LOCFIT=value:
Fitting basis set used in LMP2 and in LCCSD for integrals with up
to 2 external orbitals. If a correlation consistent basis set is used (e.g.
cc-pVTZ) the corresponding fitting basis for MP2 us used by default
(cc-pVTZ/MP2FIT). Otherwise the fitting basis set must be defined in
a preceding basis block (see section 11).
Fitting basis set used in LCCSD for integrals over 3- and 4-external
orbitals. The default is BASIS MP2 and this is usually sufficient.
However, the accurate approximation of 4-external integrals in LCCSD
requires larger fitting basis sets than LMP2. Therefore, in order to
minimize fitting errors, it is recommended to use the next larger fitting
basis, e.g., BASIS CCSD=VQZ for orbital basis VTZ.
If LOCFIT=1 local fitting is enabled. This is necessary to achieve
linear scaling in DF-LMP2 (see Refs. [11-14]). The errors introduced
by local fitting are usually very small, but there are some exceptions.
For instance, LOCFIT=1 must not be used in counterpoise calculations,
see section 29.9.8) Note that for small molecules LOCFIT=1
can be more expensive than LOCFIT=0.
For further details and options for density fitting see section 15.
30 LOCAL METHODS FOR EXCITED STATES
30.1 Local CC2 and ADC(2)
Bibliography:
General local CC2 for excited states:
[1] D. Kats, T. Korona and M. Schütz, Local CC2 electronic excitation energies for large
molecules with density fitting, J. Chem. Phys. 125, 104106 (2006).
[2] D. Kats, T. Korona and M. Schütz, Transition strengths and first-order properties of excited
states from local coupled cluster CC2 response theory with density fitting, J. Chem. Phys. 127,
064107 (2007).
Laplace transformed local CC2 for excited states:
[3] D. Kats and M. Schütz, A multistate local coupled cluster CC2 response method based on
the Laplace transform, J. Chem. Phys. 131, 124117 (2009).
[4] D. Kats and M. Schütz, Local Time-Dependent Coupled Cluster Response for Properties of
Excited States in Large Molecules, Z. Phys. Chem. 224, 601 (2010).
[5] K. Freundorfer, D. Kats, T. Korona and M. Schtz, Local CC2 response method for triplet
states based on Laplace transform: Excitation energies and first-order properties, J. Chem.
Phys., accepted, (2010).
Previous work on local methods for excited states (LEOM-CCSD):
[6] T. Korona and H.-J. Werner Local treatment of electron excitations in the EOM-CCSD
method, J. Chem. Phys. 118, 3006 (2003).
All publications resulting from use of this program must acknowledge Ref. [3] (calculations of
singlet states) and [5] (calculations of triplet states and properties).
The command LT-DF-LCC2 calls the Laplace transformed LCC2 program, and LT-DF-LADC(2)
calls LADC(2). The excited states of interest should be specified on the EOM card.