Research Information System
6th International Conference on Molecular Electronic Structure, (MES), Monastir, Tunisia, 2 - 06 September 2022, pp.15
High-accuracy computational chemistry provides a powerful
tool that can augment the body of experimental data, particularly in case of
fleeting intermediates or hazardous compounds. A number of composite schemes
have been proposed in the recent decades that aim at the accurate determination
of thermochemical properties with sub-chemical accuracy [1-5]. However, most of
these protocols defined in this manner are based on single reference methods.
In this study, we evaluate the option of integrating
the internally-contracted multireference coupled-cluster (icMRCC) method [6,7] into
a high-accuracy thermochemistry protocol. Unlike multireference configuration
interaction (MRCI), icMRCC is a size-consistent method and promises uniform
accuracy independent of the systems size. The icMRCC approach is a
straightforward generalization of the standard coupled-cluster method which
bears the option of integrating single-reference and multireference schemes.
In a first step, we evaluate the accuracy of the
icMRCC approach, addressing in particular the question how the accuracy of
icMRCCSD and icMRCCSD(T) compares to the usual coupled-cluster hierarchy for
different cases. We address the question of how certain approximations for the
triples approximation [6,7] impact the overall accuracy of the method, in
particular if large basis sets are involved. We also investigate the question
of choosing active spaces and extrapolating to the complete basis set limit for
multireference schemes. Comparison is made to the HEAT protocol for obtaining
accurate atomization and reaction energies. We also compare to experimental
results from the Active Thermochemical Tables (ATcT). [8]
Acknowledgements:
This work has been financially supported by the Scientific and Technological
Research Council of Turkey-TÜBİTAK, Grant no: TÜBİTAK-BIDEB-2219 International
Postdoctoral Research Fellowship Program (2019-1).The authors acknowledge
support by the state of Baden-Württemberg through bwHPC and the German Research
Foundation (DFG) through grant no INST 40/575-1 FUGG (JUSTUS 2 cluster).
References
[1] L. A. Curtiss, K. Raghavachan, P. C. Redfern, V. Rassolov, J.
A. Pople, J. Chem. Phys. 109, 7764-7776, 1998.
[2] A. Tajti, P. G. Szalay, A.
G. Csaszar, M. Kallay, J. Gauss, E. F. Valeev, B. A. Flowers, J.Vazquez, J. F.
Stanton, J. Chem. Phys. 121,
11599-11613 (2004).
[3] P. L. Fast, N. E. Schultz, D. G. Truhlar, J.
Phys. Chem. A, 105, 4143-4149, 2001.
[4] D. Feller, K. A. Peterson, D. A. A. Dixon, J.
Chem. Phys., 129, 204105/1-32, 2008.
[5] A. Karton, E. Rabinovich, J. M. L. Martin, B.
Ruscic, J. Chem. Phys., 125, 144108/1-17, 2006.
[6] M. Hanauer, A. Köhn, J. Chem. Phys. 136,
204107 (2004).
[7] A. Köhn, J. A. Black, Y. A. Aoto, M. Hanauer,
Mol. Phys. 118, e1743889 (2020).
[8] B. Ruscic, R. E. Pinzon,
M. L. Morton, G. von Laszewski, S. Bittner, S. G. Nijsure, K. A. Amin, M.
Minkoff, and A. F. Wagner, J. Phys. Chem. A 108, 9979, 2004.