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

Predictive coupled-cluster isomer orderings for some Si n C m (m, n ≤ 12) clusters; A pragmatic comparison between DFT and complete basis limit coupled-cluster benchmarks.Jason N. Byrd, 1, 2, a) Jesse J. The accurate determination of the preferred Si 12 C 12 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 SiC 3 to Si 12 C 12 . 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 Si 12 C 12 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.

On the onset of dust formation in AGB stars

“…Functionals such as B3LYP, M11 or PBE0 attempt to compensate for the above mentioned shortcomings of typical GGA/LDA functionals. The recent extensive benchmark study by Byrd et al (2016) confirms that the M11 functional is able to correctly identify all investigated (SiC) n ground states. Although B3LYP (Becke 1993) was found to be less accurate than M11 for SiC clusters, we also include data calculated with this widely used functional for comparison.…”

Semiconductor color-center structure and excitation spectra: Equation-of-motion coupled-cluster description of vacancy and transition-metal defect photoluminescence

“…Geometry optimizations are accellerated significanty by parallel implementations leveraging analytic gradients. In a previous study we have investigated the relative performance of a variety of DFT, MP2, and highlevel CC methods for producing geometries of several Si n C m (n ≤ m ≤ 12) molecules [66], which are expected to exhibit similar many-body physics to defects in solidstate SiC. The previous study found that MP2 and DFT with the M11 functional were good alternatives, which could closely reproduce the geometries predicted by highlevel SRCC methods.…”

“…Some TD-DFT calculations are included for comparison, but benchmarking various functionals is outside of the scope of this work so we use those deemed optimal for Si n C m (n ≤ m ≤ 12) molecules in Refs. [66] and [67] (see Sect. III for further details).…”

SinC13-n (n = 1 – 12) Clusters: An All-electron DFT Investigation

“…For larger sizes of mixed Si-C clusters, Zhu et al [17] investigated the growth patterns and electronic property of Si12C12 clusterassembled materials. In addition, by using the DFT and the coupled-cluster theory, some SinCm (m, n ≤ 12) clusters ranging in size from SiC3 to Si12C12 were predicted [18]. Most recently, silicon impacts on structure, stability and aromaticity of C20-nSin heterofullerenes (n = 1 -10) were studied in a density functional perspective [19].…”