DMRG-tailored coupled cluster method in the 4c-relativistic domain: General implementation and application to the NUHFI and NUF_3 molecules
arxiv(2024)
摘要
Heavy atom compounds represent a challenge for computational chemistry, due
to the need for simultaneous treatment of relativistic and correlation effects.
Often such systems exhibit also strong correlation which hampers the
application of perturbation theory or single-reference coupled cluster (CC)
methods. As a viable alternative, we have proposed to externally correct the CC
method using the density matrix renormalization group (DMRG) wave functions,
yielding the DMRG-tailored CC method. In a previous paper [J. Chem. Phys. 152, 174107 (2020)] we have reported a first implementation of this method in
the relativistic context, which was restricted to molecules with real double
group symmetry. In this work we present a fully general implementation of the
method, covering complex and quaternion double groups as well. The 4c-TCC
method thus becomes applicable to polyatomic molecules including heavy atoms.
For assessment of the method, we performed calculations of the chiral uranium
compound NUHFI, which was previously studied in the context of the enhancement
of parity violation effects. In particular, we performed calculations of a cut
of the potential energy surface of this molecule along the dissociation of the
N-U bond, where the system exhibits a strong multireference character. Since
there are no experimental data for NUHFI, we have performed also an analogous
study of the (more symmetric) NUF_3 molecule, where the vibrational frequency
of the N-U bond can be compared with spectroscopic data.
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