Ab initio study of boron, nitrogen, and boron--nitrogen clusters. I. Isomers and thermochemistry of B/sub 3/, B/sub 2/N, BN/sub 2/, and N/sub 3/

Journal Article · Thu Jun 01 00:00:00 EDT 1989 · J. Chem. Phys.; (United States)

OSTI ID:6182655

Martin, J M.L.; Francois, J P; Gijbels, R

For a number of different structures and states of B/sub 3/, B/sub 2/N, BN/sub 2/, and N/sub 3/, optimum geometries and harmonic spectra were obtained at the HF/6-31G* level. The relative stability of the isomers was determined using full fourth-order Moeller--Plesset theory, both with and without spin projection, as well as coupled cluster methods. Estimates for the dissociation energies are based on scaled CCD+ST(CCD) binding energies. Koopmans' vertical ionization potentials and Mulliken charge distributions, both at the UHF/6-31G* level, are quoted for the most stable isomers. B/sub 3/ is found to be an equilateral triangle in its /sup 2/A/sup '//sub 1/ ground state. B/sub 2/N has a symmetric linear arrangement in its /sup 2/..sigma../sup +//sub u/ ground state with an extremely low bending frequency (73 cm/sup -1/), and an unusually low vertical ionization potential (6.75 eV). Its asymmetric stretching (2021 cm/sup -1/) is found to be extremely intense (8782 km mol/sup -1/). BN/sub 2/ has four rather closely spaced states, of which an isosceles triangle is the absolute minimum (/sup 2/A/sub 1/ state). However, at high temperatures, an asymmetric linear arrangement (/sup 2/Pi state) is found to have equal importance, whereas a /sup 4/..sigma../sup -/ state plays a role there too. The same theoretical methods correctly predict for N/sub 3/ a symmetric linear arrangement in the /sup 2/Pi/sub g/ ground state; the spectroscopic constants are found to be in reasonable agreement with experiment. Estimated dissociation energies (expected accuracy +- 4 kcal mol/sup -1/) are: B/sub 3/ 197.9, B/sub 2/N 265.0, BN/sub 2/ 224.9, N/sub 3/ 210.1 kcal mol/sup -1/.

• Research Organization: Limburgs Universitair Centrum, Department SBM, Universitaire Campus, B-3610 Diepenbeek, Belgium and University of Antwerp (UIA), Institute for Materials Science, Department of Chemistry, Universiteitsplein 1, B-2610 Wilrijk, Belgium
• OSTI ID: 6182655
• Journal Information: J. Chem. Phys.; (United States), Vol. 90:11
• Country of Publication: United States
• Language: English

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ISOMERS
MOLECULAR ORBITAL METHOD
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