Abstract
The structural, relative stability, electronic, IR vibrational, and thermodynamic properties of asymmetric clusters (CH3FBN3)n (n = 1–6) are systematically investigated using density functional theory (DFT) method. Results show that clusters (CH3FBN3)n (n = 2–6) form a cyclic structure with a B atom and a Nα atom binding together. Five main characteristic regions are observed and assigned for the calculated IR spectra. The size-dependent second-order energy difference shows that clusters (CH3FBN3)3 and (CH3FBN3)5 have relatively higher stability and enhanced chemical inertness compared with the neighboring clusters. These two clusters may serve as the cluster-assembled materials. The variations of thermodynamic properties with temperature T or cluster size n are analyzed, respectively. Based on enthalpies in the range of 200–800 K, the formations of the most stable clusters (CH3FBN3)n (n = 2–6) from monomer are thermodynamically favorable. These data are helpful to design and synthesize other asymmetric boron azides.
Highlights
For n 2 – 6, the computed B–N bond length of 1.601–1.638 Apossesses typical character of B–N single bond, which is similar to the B–N length of other covalent boron azides previously determined, such as (F2BN3)3 (1.616 A ) [19] and (C6F5B(N3)2)3 (1.60 A ) [12]. e B−C and B−F bond lengths are in the range of 1.585–1.596 Aand 1.363–1.381 A, respectively. e computed structural parameters of the azide units in the clusters (CH3FBN3)n (n 2 – 6) are 1.240–1.255 Afor Nα−Nβ bonds, 1.128–1.133 Afor Nβ−Nc bonds, and 177.1–179.4° for Nα−Nβ−Nc bond angle
It can be seen that the charge distribution of CH3FBN3 molecule exhibits zwitterionic
Eb-c-ave set is suitable for the clusters studied here. us, in this work, we only report the relative stability of the clusters (CH3FBN3)n with the 6-31G∗ basis set. e uncorrected binding energies (Eb), corrected binding energies (Eb-c), average corrected binding energy (Eb-c-ave), and the second-order energy difference (Δ2E) are calculated using the following equations: Eb(n) nE CH3FBN3 − E CH3FBN3n, Eb−c(n) nE CH3FBN3 + 0.96 ∗ nZPE CH3FBN3 − E CH3FBN3n − 0.96 ∗ ZPE CH3FBN3n, Eb−c−ave(n)
Summary
It is important to choose an appropriate basis set to give the accurate description of clusters’ structures and energies. The size of clusters studied in this work excluded the use of a very large basis set, and all calculations were performed using the DFT-B3LYP method with the 6-31G∗ basis set [25, 26] via the Gaussian 09 program package with the default convergence thresholds [27]. E initial configurations are searched by two ways: (1) by considering the numbers of known clusters (HClBN3)n (n 1–6) in previous works [21] and (2) by placing -CH3 groups and F atoms at various substitutional sites (H or Cl) on the basis of optimized (HClBN3) geometries. Lots of rationally initial one-, two-, and three-dimensional configurations were built to seek the most stable structures. In this way, a large number of optimized isomers for the asymmetric clusters (CH3FBN3)n (n 1–6) were obtained. According to the previous study, the calculated frequencies were scaled uniformly by 0.96 to approximately correct the systematic overestimation [28]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
