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Other options can be set using the OPTION command. These options are mainly
used for testing purposes and should be used with care.
OPTION,code1=value,code2=value,
Of relevance for the CASPT2/3 program are the following options:
- IPROCS=0
- (Default). Calculation uses uncontraced singles with RS2.
Note: The IPROCS option must not be used with RS2C.
- IPROCS=1
- Non-interacting singles are projected out during update. This is
an approximate procedure which should be used with care.
- IPROCS=2
- The singles are fully internally contracted in RS2. This is
achieved via a projection operator during the coefficient update and may be inefficient.
- IPROCS=3
- Singles with one or two holes in the closed-shells are are internally
contracted in RS2 using a projection operator.
- IPROCI=0
- (Default). Calculation uses uncontraced internals with RS2.
- IPROCI=1
- Internals with two holes in the inactive space are internally contracted
in RS2 using a projection operator.
- IPROCC=1
- Reproduces with RS2 the RS2C result using projection operators.
This is equivalent to IPROCS=3 and IPROCI=1.
- IFDIA=0
- (Default). All off-diagonal elements of the effective Fock matrix are included.
- IFDIA=1
- The internal-external block of the Fock-matrix is neglected. This eliminates the
single-pair coupling.
- IFDIA=2
- All off-diagonal elements of the Fock matrix are neglected. This corresponds
to CASPT2D of Andersson et al. Note: in this case the result is not invariant to rotations
among active orbitals!
- IHINT=0
- (Default). Only one-electron integrals are used in the zeroth-order Hamiltonian
for all interactions.
- IHINT=1
- The all-internal two-electron integrals are used in the zeroth-order Hamiltonian
for the internal-internal and single-single interactions.
- IHINT=2
- The all-internal two-electron integrals in the zeroth-order Hamiltonian
are used for the internal-internal, single-single, and pair-pair interactions. Using
IHINT=2 and IDFIA=1 corresponds to
Dyall's CAS/A method for the case that CASSCF references with no closed-shells (inactive orbitals) are used.
Note that this requires more CPU time than a standard CASPT2 calculation. Moreover,
convergence of the CAS/A method is often slow (demominator shifts specified on a SHIFT card
may be helpful in such cases). In general, we do not recommend the use of IHINT with nonzero
values. The IHINT option must not be used with RS2C.
- NOREF=1
- (Default). Interactions between reference configurations and singles
are omitted.
- NOREF=0
- Interactions between reference configurations and singles are included.
This causes a relaxation of the reference coefficients but may lead to intruder-state problems.
- IMP3=2
- After CASPT2 do variational CI using all internal configurations and the first-order
wavefunctions of all states as a basis. In this case the second-order energy will correspond to the
variational energy, and the third-order energy approximately to a Davdison-corrected energy.
This is useful in excited state calculations with near-degeneracy situations.
- SHIFTE0=xxyy
- Special option for setting level shift in RS2C.
If
:
level shift for
space,
= level shift for
space.
If
: ABS
level shift for all spaces (equivalent to SHIFT option on RS2C card).
Next: 22 MØLLER PLESSET PERTURBATION
Up: 21 MULTIREFERENCE RAYLEIGH SCHRÖDINGER
Previous: 21.5 Integral direct calculations
P.J. Knowles and H.-J. Werner
molpro-support@tc.bham.ac.uk
Mar 8, 2000