Performance of Block Correlated Coupled Cluster Method with the CASSCF Reference Function for Carbon–Carbon Bond Breaking in Hydrocarbons

Fang, Tao; Li, Shuhua

doi:10.1007/978-90-481-2596-8_11

Cited by 3 publications

(4 citation statements)

References 106 publications

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“…With this basis set, the coupled-cluster with single and double and perturbative triple excitations (CCSDT) PES of this molecule is available [37] for comparison, which should be very close to the FCI PES. The results are listed in [18,20,24,25], one can see that in most cases the CAS-BCCC4 results are comparable to the MR-CISD+ Q results, and more accurate than those from CASPT2 and MR-CISD.…”

Section: Illustrative Applicationssupporting

confidence: 60%

“…The CAS-BCCC4 method has been applied to investigate the potential energy surfaces for several model and real systems, and its performance has been carefully assessed [18,20,24,25]. Here, we will show the results of various theoretical methods for two typical molecules, the H 8 model and F 2 .…”

Section: Illustrative Applicationsmentioning

confidence: 99%

“…The CAS-BCCC4 method has been shown to provide satisfactory descriptions for a variety of chemical problems, in which the multireference character is significant. For example, our method has been applied to compute the potential energy surfaces (PESs) of bond breaking processes, the singlet-triplet (S-T) gaps in diradicals, the activation barriers for some isomerization reactions, spectroscopic constants in diatomic molecules, and excitation energies for low-lying excited states [18][19][20][21][22][23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

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Comparison of some multireference electronic structure methods in illustrative applications

2010

Sci. China Chem.

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The performances of several multireference electronic structure methods including complete active space self-consistent field (CASSCF)-based second-order perturbation theory (CASPT2), multireference configuration interaction with single and double excitations (MR-CISD), MR-CISD with the Davidson correction (MR-CISD+Q), and the CASSCF-based block-correlated coupled cluster method (CAS-BCCC4) we developed recently are compared by applying them to study several different chemical problems involving computation of ground state potential energy surfaces, the singlet-triplet gaps in diradicals, reaction barriers, and the excitation energies of low-lying excited states. Comparison with the results from other highly accurate theoretical methods or the available experimental data demonstrate that for all the problems studied, the overall performance of CAS-BCCC4 is competitive with that of MR-CISD+Q, and better than that of CASPT2 and MR-CISD methods. Thus the CAS-BCCC4 approach is expected to be a promising theoretical method for quantitative descriptions of the electronic structures of molecules with noticeable multireference character. multireference, block correlated coupled cluster, CASPT2, MR-CISD

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Section: Illustrative Applicationssupporting

confidence: 60%

Section: Illustrative Applicationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparison of some multireference electronic structure methods in illustrative applications

2010

Sci. China Chem.

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“…The last issues that we want to analyze are the property of size-consistency and the ability of the various ansätze to properly describe the molecular fragmentation without introducing any kind of spin contamination. In the case of the breaking of the single or double bonds of 1,3-butadiene, none of the methods reported in Table , and based on restricted single references, can properly describe the molecular fragmentations, not even CCSD(T). , …”

Section: Results and Discussionmentioning

confidence: 99%

π-Conjugation in trans-1,3-Butadiene: Static and Dynamical Electronic Correlations Described through Quantum Monte Carlo

Barborini

Guidoni

2015

J. Chem. Theory Comput.

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We investigate the effects of the static and dynamical electronic correlations on the level of conjugation of the trans-1,3-butadiene molecule through Quantum Monte Carlo methods applied to an Antisymmetrized Geminal Power (AGP) wave function, with a Jastrow factor similar to the Gutzwiller ansatz. The degree of conjugation is measured through the convergence of the structural properties of 1,3-butadiene and in particular of the Bond Length Alternation (BLA), that is the difference between the lengths of the single and double carbon bonds. After verifying the different roles of the Fermionic AGP part of our wave function and of the Jastrow factor in recovering electronic correlation, we study the effects of a constrained Active Space AGP (AGPAS), similar to that used in the Complete Active Space (CAS) representation. Through this AGPAS, we are able to identify the effect of the limited active space on the degree of conjugation, showing that in the limit of infinite active space the structural properties converge exactly to those of the atomic AGP, giving a BLA for 1,3-butadiene around 0.1244(5) Å.

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Search of truncation of (N−1) electron basis containing full connected triple excitations in computing main and satellite ionization potentials via Fock‐space coupled cluster approach

Adhikari¹,

Chattopadhyay

et al. 2013

J Comput Chem

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A valence-universal multireference coupled cluster (VUMRCC) theory, realized via the eigenvalue independent partitioning (EIP) route, has been implemented with full inclusion of triples excitations for computing and analyzing the entire main and several satellite peaks in the ionization potential spectra of several molecules. The EIP-VUMRCC method, unlike the traditional VUMRCC theory, allows divergence-free homing-in to satellite roots which would otherwise have been plagued by intruders, and is thus numerically more robust to obtain more efficient and dependable computational schemes allowing more extensive use of the approach. The computed ionization potentials (IPs) as a result of truncation of the (N-1) electron basis manifold involving virtual functions such as 2h-p and 3h-2p by different energy thresholds varying from 5 to 15 a.u. with 1 a.u. intervals as well as thresholds such as 20, 25, and 30 a.u. have been carefully looked into. Cutoff at around 25 a.u. turns out to be an optimal threshold. Molecules such as C2H4 and C2H2 (X = D,T), and N2 and CO (X = D,T,Q) with Dunning's cc-pVXZ bases have been investigated to determine all main and 2h-p shake-up and 3h-2p double shake-up satellite IPs. We believe that the present work will pave the way to a wider application of the method by providing main and satellite IPs for some problematic N-electron closed shell systems.

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Performance of Block Correlated Coupled Cluster Method with the CASSCF Reference Function for Carbon–Carbon Bond Breaking in Hydrocarbons

Cited by 3 publications

References 106 publications

Comparison of some multireference electronic structure methods in illustrative applications

Comparison of some multireference electronic structure methods in illustrative applications

π-Conjugation in trans-1,3-Butadiene: Static and Dynamical Electronic Correlations Described through Quantum Monte Carlo

Search of truncation of (N−1) electron basis containing full connected triple excitations in computing main and satellite ionization potentials via Fock‐space coupled cluster approach

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