32 THE MRCI PROGRAM

Multiconfiguration reference internally contracted configuration interaction

Bibliography:

H.-J. Werner and P.J. Knowles, J. Chem. Phys. 89, 5803 (1988).

P.J. Knowles and H.-J. Werner, Chem. Phys. Lett. 145, 514 (1988).

For excited state calculations:

P. J. Knowles and H.-J. Werner, Theor. Chim. Acta **84**, 95 (1992).

For explicitly correlated MRCI (MRCI-F12):

T. Shiozaki, G. Knizia, and H.-J. Werner, J. Chem. Phys. **134**, 034113 (2011);

T. Shiozaki and H.-J. Werner, J. Chem. Phys. **134**, 184104 (2011);

T. Shiozaki and H.-J. Werner, Mol. Phys. **111**, 607 (2013).

All publications resulting from use of the corresponding methods must acknowledge the above.

The first internally correlated MRCI program was described in:

H.-J. Werner and E.A. Reinsch, J. Chem. Phys. 76, 3144 (1982).

H.-J. Werner, Adv. Chem. Phys. 59, 1 (1987).

The command `CI` or `CI-PRO` or `MRCI` calls the MRCI program.

The command `MRCI-F12` calls the explicitly correlated MRCI-F12 program.

The command `CISD` calls fast closed-shell CISD program.

The command `QCI` calls closed-shell quadratic CI program.

The command `CCSD` calls closed-shell coupled-cluster program.

The following options may be specified on the command line:

`NOCHECK`- Do not stop if no convergence.
`DIRECT`- Do calculation integral direct.
`NOSING`- Do not include singly external configurations.
`NOPAIR`- Do not include doubly external configurations (not valid for single reference methods).
`MAXIT=`*value*- Maximum number of iterations.
`MAXITI=`*value*- Maximum number of microiterations (for internals).
`SHIFTI=`*value*- Denominator shift for update of internal configurations.
`SHIFTS=`*value*- Denominator shift for update of singles.
`SHIFTP=`*value*- Denominator shift for update of doubles.
`THRDEN=`*value*- Convergence threshold for the energy.
`THRVAR=`*value*- Convergence threshold for the CI-vector. This applies to the square sum of the changes of the CI-coefficients.
`SWAP|NOSWAP`- If
`SWAP`is given, the MRCI wavefunctions are reordered according to maximum overlap with the reference functions (this only applies in multi-state calculations). The default is`NOSWAP`, i.e. the states are ordered according to increasing MRCI energy. `ROTREF=`*value*- If
*value*=0 the cluster corrections are not printed for the rotated reference energies (cf. Section 32.24). If*value*=1 all corrections are printed. If*value*=2 (default) the reference are transformed to maximize the overlap with the final MRCI wavefunctions, and the cluster corrections are computed using these rotated reference states. If*value*=-1 the 2009.1 behaviour is recovered. `CIREC=`*record*-
If given, the program attempts reading the reference vectors from a previous CASSCF calculation.
The vectors must have been saved in the CASSCF using
`SAVE,CIREC=`*record*This will only work if the active spaces in the CASSCF and MRCI are the same.

- 32.1 Introduction
- 32.2 Specifying the wavefunction
- 32.3 Coupled Electron Pair Approximation
- 32.4 Coupled Pair Functional (ACPF, AQCC)
- 32.5 Projected excited state calculations
- 32.6 Transition matrix element options
- 32.7 Convergence thresholds
- 32.8 Level shifts
- 32.9 Maximum number of iterations
- 32.10 Restricting numbers of expansion vectors
- 32.11 Selecting the primary configuration set
- 32.12 Canonicalizing external orbitals
- 32.13 Saving the wavefunction
- 32.14 Starting wavefunction
- 32.15 One electron properties
- 32.16 Transition moment calculations
- 32.17 Saving the density matrix
- 32.18 Natural orbitals
- 32.19 Miscellaneous options
- 32.20 Miscellaneous parameters
- 32.21 Miscellaneous thresholds
- 32.22 Print options
- 32.23 Examples
- 32.24 Cluster corrections for multi-state MRCI
- 32.25 Explicitly correlated MRCI-F12