Thermochemistry and Electronic Structure of Small Boron and Boron Oxide Clusters and Their Anions

Abstract

Thermochemical properties of a set of small boron (B(n)) and boron oxide (B(n)O(m)) clusters, with n = 1-4 and m = 0-3, their anions, and the B(4)(2-) dianion, were calculated by using coupled-cluster theory CCSD(T) calculations with the aug-cc-pVnZ (n = D, T, Q, 5) basis sets extrapolated to the complete basis set limit with additional corrections. Enthalpies of formation, bond dissociation energies, singlet-triplet or doublet-quartet separation gaps, adiabatic electron affinities (EA), and both vertical electron attachment and detachment energies were evaluated. The predicted heats of formation show agreement close to the error bars of the literature results for boron oxides with the largest error for OBO. Our calculated adiabatic EAs are in good agreement with recent experiments: B (calc, 0.26 eV; exptl, 0.28 eV), B(2) (1.95, 1.80), B(3) (2.88, 2.820 +/- 0.020), B(4) (1.68, 1.60 +/- 0.10), BO (2.50, 2.51), BO(2) (4.48, 4.51), BOB (0.07), B(2)O(2) (0.37), B(3)O (2.05), B(3)O(2) (2.94, 2.94), B(4)O (2.58), and B(4)O(2) (3.14, 3.160 +/- 0.015). The BO bond is strong, so this moiety is maintained in most of the clusters. Thermochemical parameters of clusters are not linearly additive with respect to the number of B atoms. The EA tends to be larger in the dioxides. The growth mechanism of small boron oxides should be determined by a number of factors: (i) formation of BO bonds, (ii) when possible, formation of a cyclic B(3) or B(4), and (iii) combination of a boron cycle and a BO bond. When these factors compete, the strength of the BO bonds tends to compensate the destabilization arising from a loss of binding in the cyclic boron clusters, in such a way that a linear boron oxide prevails. When the B(2) moiety is present in these linear clusters, the oxide derivatives prefer a high spin state.

Structure and properties of the aluminum borates Al(BO2)n and Al(BO2)n−, (n = 1–4)

“…The value of the BO 2 EA ad obtained using an electron propagator method and the 6-311þG(2df) basis set is 4.65 eV, [73] and the OVGF value obtained using an augmented double-1 basis set [74] is 4.7 eV. The value of 4.53 eV was obtained in the recent CCSD(T) computations [75] performed using an augmented quadruple-1 basis set and the B3LYP optimized geometry.…”

Electronic Structures and Thermochemical Properties of the Small Silicon‐Doped Boron Clusters BnSi (n=1–7) and Their Anions

“…[32][33][34] Enthalpies of formation for the global minima were evaluated from the corresponding total atomization energies (TAE). [35] Two sets of calculations were performed, including the coupled-cluster theory whose total energies were extrapolated to the complete basis-set limit, CCSD(T)/CBS, as previously used for the series of small boron clusters, [36,37] and the composite G4 approach. [38] In the CCSD(T)/CBS approach, geometrical parameters were fully optimized using either the coupled-cluster CCSD(T) theory [39] (for small species B n Si 0/À with n = 1-3), or the secondorder perturbation theory (MP2) levels (for the larger species with n = 4-7) using the correlation consistent aug-cc-pVTZ basis set.…”

“…To consider the effects of Si doping, binding-energy values of the B n host are evaluated from total atomic energies (TAE) of the B n clusters (obtained from refs. [36] and [37] at the same CBS method). Binding-energy values of B n clusters are reported in Table S3 (Supporting Information), their plot is also shown in Figure 3.…”

“…[36] and [37]; these were obtained using the same CCSD(T)/CBS method. For the neutrals, the dissociation energies obtained from two channels are approximate, except for B 4 For all the four channels considered, the D e value of B 7 Si is remarkably high, which again indicates its high thermodynamic stability.…”

“…[51] The rationale for this selection was discussed in our previous work. [36,37] We thus obtained heats of formation at 298 K by following the classical thermochemical procedure. [52] The calculated heats of formation at 0 K were used to evaluate the adiabatic detachment energy and other energetic quantities.…”