title: Predictive coupled-cluster isomer orderings for some SinCm (m, n ≤ 12) clusters: A pragmatic comparison between DFT and complete basis limit coupled-cluster benchmarks.
abstract: 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 the 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 coupled-cluster theory with singles and doubles extrapolation with triple-ζ (T) correlation, the closo Si12C12 isomer is identified to be the preferred isomer in the support of previous calculations [X. F. Duan and L. W. Burggraf, J. Chem. Phys. 142, 034303 (2015)]. 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 are found to be an excellent balance between efficiency and accuracy.
authors.affiliation: Quantum Theory Project, University of Florida, Gainesville, Florida 32611, USA.
authors.forename: Jason N
authors.initials: JN
authors.lastname: Byrd
authors.affiliation: Quantum Theory Project, University of Florida, Gainesville, Florida 32611, USA.
authors.forename: Jesse J
authors.initials: JJ
authors.lastname: Lutz
authors.affiliation: Quantum Theory Project, University of Florida, Gainesville, Florida 32611, USA.
authors.forename: Yifan
authors.initials: Y
authors.lastname: Jin
authors.affiliation: Quantum Theory Project, University of Florida, Gainesville, Florida 32611, USA.
authors.forename: Duminda S
authors.initials: DS
authors.lastname: Ranasinghe
authors.affiliation: Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Montgomery
authors.affiliation: Quantum Theory Project, University of Florida, Gainesville, Florida 32611, USA.
authors.forename: Ajith
authors.initials: A
authors.lastname: Perera
authors.affiliation: Air Force Institute of Technology, Wright-Patterson Air Force Base, Ohio 45433, USA.
authors.forename: Xiaofeng F
authors.initials: XF
authors.lastname: Duan
authors.affiliation: Air Force Institute of Technology, Wright-Patterson Air Force Base, Ohio 45433, USA.
authors.forename: Larry W
authors.initials: LW
authors.lastname: Burggraf
authors.affiliation: Quantum Theory Project, University of Florida, Gainesville, Florida 32611, USA.
authors.forename: Beverly A
authors.initials: BA
authors.lastname: Sanders
authors.affiliation: Quantum Theory Project, University of Florida, Gainesville, Florida 32611, USA.
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Bartlett