The Intricate Case of Tetramethyleneethane: A Full Configuration Interaction Quantum Monte Carlo Benchmark and Multireference Coupled Cluster Studies

Libor Veis, Andrej Antalík, O. Legeza, Ali Alavi, Jiří Pittner

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

We have performed a full configuration interaction (FCI) quality benchmark calculation for the tetramethyleneethane molecule in the cc-pVTZ basis set employing a subset of complete active space second order perturbation theory, CASPT2(6,6), natural orbitals for the FCI quantum Monte Carlo calculation. The results are in an excellent agreement with the previous large scale diffusion Monte Carlo calculations by Pozun et al. and available experimental results. Our computations verified that there is a maximum on the potential energy surface (PES) of the ground singlet state (1A) 45° torsional angle, and the corresponding vertical singlet-triplet energy gap is 0.01 eV. We have employed this benchmark for the assessment of the accuracy of Mukherjee's coupled clusters with up to triple excitations (MkCCSDT) and CCSD tailored by the density matrix renormalization group method (DMRG). Multireference MkCCSDT with CAS(2,2) model space, though giving good values for the singlet-triplet energy gap, is not able to properly describe the shape of the multireference singlet PES. Similarly, DMRG(24,25) is not able to correctly capture the shape of the singlet surface, due to the missing dynamic correlation. On the other hand, the DMRG-tailored CCSD method describes the shape of the ground singlet state with excellent accuracy but for the correct ordering requires computation of the zero-spin-projection component of the triplet state (3B1).

Original languageEnglish
Pages (from-to)2439-2445
Number of pages7
JournalJournal of Chemical Theory and Computation
Volume14
Issue number5
DOIs
Publication statusPublished - May 8 2018

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configuration interaction
renormalization group methods
Potential energy surfaces
Ground state
Energy gap
potential energy
ground state
atomic energy levels
set theory
perturbation theory
projection
tetramethyleneethane
orbitals
Molecules
excitation
molecules

ASJC Scopus subject areas

  • Computer Science Applications
  • Physical and Theoretical Chemistry

Cite this

The Intricate Case of Tetramethyleneethane : A Full Configuration Interaction Quantum Monte Carlo Benchmark and Multireference Coupled Cluster Studies. / Veis, Libor; Antalík, Andrej; Legeza, O.; Alavi, Ali; Pittner, Jiří.

In: Journal of Chemical Theory and Computation, Vol. 14, No. 5, 08.05.2018, p. 2439-2445.

Research output: Contribution to journalArticle

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