21 MULTIREFERENCE RAYLEIGH SCHRÖDINGER PERTURBATION THEORY
H.-J. Werner, Mol. Phys. 89, 645-661 (1996)
New internally contracted RS2C:
P. Celani and H.-J. Werner, J. Chem. Phys. 112, 5546 (2000)
All publications resulting from use of this program must acknowledge the above.
are used to perform second or third-order
perturbation calculations. RS3 always includes RS2 as a first step. For
closed-shell single-reference cases, this is
equivalent to MP2 or MP3 (but a different program is used). RS2C
calls a new more efficient second-order program (see below), which should normally
be used if third-order is not required (note that RS3C is not available).
for RS2 an explicitly correlated version as described in
T. Shiozaki and H.-J. Werner, J. Chem. Phys. 133, 141103 (2010)
is available. This is called using the command
Options can be the following:
In addition, all valid options for MRCI can be given (see Sect. 20).
- Use modified zeroth order Hamiltonian, see section 21.4
- Level shift, see section 21.5
- IPEA shift proposed by G. Ghigo, B. O. Roos, and
P.A. Malmqvist, Chem. Phys. Lett. 396, 142 (2004), see section 21.5.
- Invokes multi-state (MS-CASPT2) treatment using nstates states.
See section 21.3 for more details.
- MS-CASPT2 method of Finley et al. CPL 288, 299 (1998)
- Extended multi-state CASPT2 (XMS-CASPT2) method as described in J. Chem. Phys. 135, 081106 (2011).
fully invariant treatment of level shifts (recommended).
- XMS-CASPT2 method; level shift is only applied to the diagonal of H0.
- Root number to be optimized in geometry optimization. This refers
to the nstates included in the MS-CASPT2.
See section 21.7 for more details.
- Record for saving the effective Hamiltonian in MS-CASPT2 calculations.
If this is not given, a default record will be used (recommended).
- (logical) Initializes a MS-CASPT2 with single state reference functions, see section 21.3
- (logical) Flags an approximate gradient calculation without CP-CASPT2; see section 21.7 for details.