Eur. Phys. J. D 19, 339-348 (2002)
https://doi.org/10.1140/epjd/e20020097

Magic numbers in heteroatom-containing carbon monocycles

¹ Faculté des Sciences, Département de Physique, 33 rue Saint-Leu, 80039 Amiens Cedex, France
² Laboratoire de Physique des Lasers, Atomes et Molécules, CNRS, CERLA, Université de Lille 1, bâtiment P5, 59655 Villeneuve d'Ascq Cedex, France

Corresponding author: ^a pascoli@u-picardie.fr

Received: 13 December 2001
Revised: 26 February 2002
Published online: 15 June 2002

Abstract

Geometries, electronic structures and energetics of heteroatom-doped carbon clusters of the type C_nX⁺ (, Si; n=9–15) have been investigated by means of the B3LYP (Becke 3-parameter-Lee-Yang-Parr) density functional method. The C_nB⁺ (n=9–15) cations are predicted to be planar monocycles while in the C_nSi⁺ cations a linear form is favored for C₉Si⁺ and structural transition from linear to planar ring-shape structure occurs at n=10. Another difference between the two C_nB⁺ and C_nSi⁺ series is that in the C_nB⁺ cations the boron atom is found to be incorporated into monocyclic structures whereas in the C_nSi⁺ cations the silicon atom is bound to the outside of the carbon monocycle. More generally it is predicted that unlike first-row atoms such as B and N which can be easily networked into monocycles, second-row atoms such as Si, P and S are attached outside the carbon ring in capping position over two carbons. Incremental binding energy diagrams are also produced for the C_nB⁺ and C_nSi⁺ cations. It is shown that maxima of stability appear at n=10 and 14 for the C_nB⁺ cations in very close agreement with the experimental features. In contrast a clear theory-versus-experiment discrepancy has been evidenced in the C_nSi⁺ cluster series where B3LYP results clearly contradict the experiments concerning the relative stability of these species. Possible explanations for this discrepancy are suggested.