| Autor: |
Aoto, Yuri Alexandre, Köhn, Andreas |
| Předmět: |
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| Zdroj: |
Journal of Chemical Physics; 2016, Vol. 144 Issue 7, p1-10, 10p, 7 Graphs |
| Abstrakt: |
The internally contracted multireference coupled cluster (icMRCC) theory is reexamined in a multistate framework. The new derivation starts from the Bloch equations employing a wave operator similar to the one originally employed by Jeziorski and Monkhorst [Phys. Rev. A 24, 1668 (1981)], but allows for a multideterminantal model-space basis. The resulting working equations are a generalization of state-universal multireference coupled-cluster (SU-MRCC) theory. In the case of truncated cluster operators, energies and wave functions depend on the choice of the model-space basis. It is shown that the state-specific solutions of the original icMRCC theory exactly diagonalize the effective Hamiltonian of the multistate theory and thus decouple the multistate equations. While this in principle means that icMRCC is a multistate theory, we find that truncated icMRCC theory still shows minor artifacts close to avoided crossings, which can be removed by considering a true multistate ansatz. The results also shed new light on the orbital variance of the original SU-MRCC theory. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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