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Poster De Conférence Année : 2022

Assessing MP2 frozen natural orbitals for relativistic electronic structure

Résumé

The O(N6) computation cost is a bottleneck preventing performing Coupled-Cluster (CC) on large systems, particularly when employing 4- component based relativistic Hamiltonians, for which in practice one often uses uncontracted basis set generating large virtual molecular orbitalspaces.
The canonical Hartree-Fock (HF) orbitals are not the most compact representation for post HF method. On other hand, using natural orbital is an efficient way to reduce the orbital space and maintains most of the accuracy. We therefore implemented the MP2 frozen natural orbital (FNO) method [1] in the Exacorr code [2], with the particularity that our implementation can generate both complex and quaternion FNOs, and also express these in AO basis. It also allows us to obtain CCSD natural orbitals on AO basis, which can be subsequently used in analysis. We have investigated the orbital truncation errors in both correlation energy and molecular properties including dipole, quadrupole moment, electric filed gradient, for hydrogen halides HX (X=F, Cl, Br, I, At, Ts), and parity violation for the H2X2 (X= O, S, Se, Te, Po) molecules. We find that FNO indeed accelerates rapidly the correlation energy convergence. For properties, truncated FNO spaces seem to slightly outperform canonical HF orbitals, and to provide reliable estimates for the molecular properties obtained for complete virtual spaces [3]. Reference [1] T. L. Barr, E. R. Davidson, Phys. Rev. A 1970, 1, 644; A. G. Taube, R. J. Bartlett, J. Chem. Phys. 2008, 128, 164101
[2] J. V. Pototschnig, A. Papadopoulos, D. I. Lyakh, M. Repisky, L. Halbert, A. S. P. Gomes, H- JAa. Jensen, L. Visscher, J. Chem. Theory. Comput. 2021, 17, 5509
[3] X. Yuan, L. Visscher, ASP. Gomes, J. Chem. Phys. 2022, arXiv:2202.01146
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Dates et versions

hal-03906582 , version 1 (19-12-2022)

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  • HAL Id : hal-03906582 , version 1

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Xiang Yuan, Lucas Visscher, André Severo Pereira Gomes. Assessing MP2 frozen natural orbitals for relativistic electronic structure. Workshop of the GDR quantum gases, Oct 2022, Lille, France. , 2022. ⟨hal-03906582⟩
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