Description
These method keywords request coupled cluster calculations [ Bartlett78 R. J. Bartlett and G. D. Purvis III, “Many-body perturbation-theory, coupled-pair many-electron theory, and importance of quadruple excitations for correlation problem,” Int. J. Quantum Chem., 14 (1978) 561-81. DOI: ], using double substitutions from the Hartree-Fock determinant for CCD [ Pople78 J. A. Pople, R. Krishnan, H. B. Schlegel, and J. S. Binkley, “Electron Correlation Theories and Their Application to the Study of Simple Reaction Potential Surfaces,” Int. J. Quantum Chem., 14 (1978) 545-60. DOI: ], or both single and double substitutions for CCSD [ Cizek69 J. Cížek, in Advances in Chemical Physics, Ed. P. C. Hariharan, Vol. 14 (Wiley Interscience, New York, 1969) 35. DOI: , Purvis82 G. D. Purvis III and R. J. Bartlett, “A full coupled-cluster singles and doubles model - the inclusion of disconnected triples,” J. Chem. Phys., 76 (1982) 1910-18. DOI: , Scuseria88 G. E. Scuseria, C. L. Janssen, and H. F. Schaefer III, “An efficient reformulation of the closed-shell coupled cluster single and double excitation (CCSD) equations,” J. Chem. Phys., 89 (1988) 7382-87. DOI: , Scuseria89 G. E. Scuseria and H. F. Schaefer III, “Is coupled cluster singles and doubles (CCSD) more computationally intensive than quadratic configuration-interaction (QCISD)?” J. Chem. Phys., 90 (1989) 3700-03. DOI: ]. CC and QCID are synonyms for CCD. RO may be combined with CCSD for a restricted open-shell energy calculation [ Watts93 J. D. Watts, J. Gauss, and R. J. Bartlett, “Coupled-cluster methods with noniterative triple excitations for restricted open-shell Hartree-Fock and other general single determinant reference functions. Energies and analytical gradients,” J. Chem. Phys., 98 (1993). DOI: ].
入力
Options
FC
All frozen core options are available with this keyword; a frozen core calculation is the default. See the discussion of the FC options for full information.
T
Include triple excitations non-iteratively [ Purvis82 G. D. Purvis III and R. J. Bartlett, “A full coupled-cluster singles and doubles model - the inclusion of disconnected triples,” J. Chem. Phys., 76 (1982) 1910-18. DOI: , Pople87 J. A. Pople, M. Head-Gordon, and K. Raghavachari, “Quadratic configuration interaction - a general technique for determining electron correlation energies,” J. Chem. Phys., 87 (1987) 5968-75. DOI: ] (CCSD only). CCSD-T is a synonym for CCSD(T).
E4T
Used with the T option to request inclusion of triple excitations for both the complete MP4 as well as CCSD(T).
T1Diag
Computes the T1 diagnostic of T. J. Lee and coworkers [ Lee89 T. J. Lee and P. R. Taylor, “A diagnostic for determining the quality of single-reference electron correlation methods,” Int. J. Quantum Chem., Quant. Chem. Symp., S23 (1989) 199-207. DOI: ] (CCSD only).
Conver=N
Sets the convergence calculations to 10-N on the energy and 10-(N-2) on the wavefunction. The default is N=7 for single points and N=8 for gradients.
MaxCyc=N
Specifies the maximum number of cycles for CCSD calculations.
TWInCore
Whether to store amplitudes and products in memory during higher-order post-SCF calculations. The default is to store these if possible, but to run off disk if memory is insufficient. TWInCore causes the program to terminate if these can not be held in memory, while NoTWInCore prohibits in-memory storage.
SaveAmplitudes
Saves the converged amplitudes in the checkpoint file for use in a subsequent calculation (e.g., using a larger basis set). Using this option results in a very large checkpoint file, but also may significantly speed up later calculations.
ReadAmplitudes
Reads the converged amplitudes from the checkpoint file (if present). Note that the new calculation can use a different basis set, method (if applicable), etc. than the original one.
オプション
Availability
Analytic energies and gradients for CCD and CCSD, numerical gradients for CCSD(T), and numerical frequencies for all methods.
The restricted open-shell (RO) method is available for CCSD and CCSD(T) energy calculations.
適用範囲
Related Keywords
関連キーワード
Examples
The Coupled Cluster energy appears in the output as follows following the final correlation iteration. The CCSD energy is given in the first line below, and the final line reports the energy with triples included:
Wavefunction amplitudes converged. E(Corr)= -75.001924366 … CCSD(T)= -0.75002048348D+02
The CCSD energy is labeled E(CORR), and the energy including the non-iterative triples contribution is given in the final line.
実例
These method keywords request coupled cluster calculations [ Bartlett78 R. J. Bartlett and G. D. Purvis III, “Many-body perturbation-theory, coupled-pair many-electron theory, and importance of quadruple excitations for correlation problem,” Int. J. Quantum Chem., 14 (1978) 561-81. DOI: ], using double substitutions from the Hartree-Fock determinant for CCD [ Pople78 J. A. Pople, R. Krishnan, H. B. Schlegel, and J. S. Binkley, “Electron Correlation Theories and Their Application to the Study of Simple Reaction Potential Surfaces,” Int. J. Quantum Chem., 14 (1978) 545-60. DOI: ], or both single and double substitutions for CCSD [ Cizek69 J. Cížek, in Advances in Chemical Physics, Ed. P. C. Hariharan, Vol. 14 (Wiley Interscience, New York, 1969) 35. DOI: , Purvis82 G. D. Purvis III and R. J. Bartlett, “A full coupled-cluster singles and doubles model - the inclusion of disconnected triples,” J. Chem. Phys., 76 (1982) 1910-18. DOI: , Scuseria88 G. E. Scuseria, C. L. Janssen, and H. F. Schaefer III, “An efficient reformulation of the closed-shell coupled cluster single and double excitation (CCSD) equations,” J. Chem. Phys., 89 (1988) 7382-87. DOI: , Scuseria89 G. E. Scuseria and H. F. Schaefer III, “Is coupled cluster singles and doubles (CCSD) more computationally intensive than quadratic configuration-interaction (QCISD)?” J. Chem. Phys., 90 (1989) 3700-03. DOI: ]. CC and QCID are synonyms for CCD. RO may be combined with CCSD for a restricted open-shell energy calculation [ Watts93 J. D. Watts, J. Gauss, and R. J. Bartlett, “Coupled-cluster methods with noniterative triple excitations for restricted open-shell Hartree-Fock and other general single determinant reference functions. Energies and analytical gradients,” J. Chem. Phys., 98 (1993). DOI: ].