Predictive Coupled-cluster Isomer Orderings for Some SinCm (m, n ≤ 12) Clusters: A Pragmatic Comparison between DFT and Complete Basis Limit Coupled-cluster Benchmarks

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The accurate determination of the preferred Si12C12 isomer is important to guide experimental efforts directed towards synthesizing SiC nano-wires and related polymer structures which are anticipated to be highly efficient exciton materials for opto-electronic devices. In order to definitively identify preferred isomeric structures for silicon carbon nano-clusters, highly accurate geometries, energies and harmonic zero point energies have been computed using coupled-cluster theory with systematic extrapolation to the complete basis limit for set of silicon carbon clusters ranging in size from SiC3 to Si12C12. It is found that post-MBPT(2) correlation energy plays a significant role in obtaining converged relative isomer energies, suggesting that predictions using low rung density functional methods will not have adequate accuracy. Utilizing the best composite coupled-cluster energy that is still computationally feasible, entailing a 3-4 SCF and CCSD extrapolation with triple-ζ (T) correlation, the closo Si12C12 isomer is identified to be the preferred isomer in support of previous calculations [J. Chem. Phys. 2015, 142, 034303]. Additionally we have investigated more pragmatic approaches to obtaining accurate silicon carbide isomer energies, including the use of frozen natural orbital coupled-cluster theory and several rungs of standard and double-hybrid density functional theory. Frozen natural orbitals as a way to compute post MBPT(2) correlation energy is found to be an excellent balance between efficiency and accuracy.


© 2016 Author(s). Published by AIP Publishing.

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The published version of record appears in Journal of Chemical Physics as cited below. The published version is available by subscription.


Version of record: 10.1063/1.4955196 ;

arxiv: 10.48550/arXiv.1606.06713

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Journal of Chemical Physics