Journal of Structural Chemistry. Vol. 54, No. 1, pp. 32-39, 2013 Original Russian Text Copyright © 2013 by Q. Y. Xia, D. X. Ma, D. J. Li, W. W. Zhao

THEORETICAL STUDY ON THE STRUCTURES

AND PROPERTIES OF (Br2AlN3)n (n = 1-4) CLUSTERS

©Q. Y. Xia, D. X. Ma, D. J. Li, and W. W. Zhao DOI: 10.1134/S0022476613010058

To look for the single-source precursors, the structures and properties of (Br2AlN3)n (n = 1-4) clusters are

studied at the B3LYP/6-311+G* level. The optimized (Br2AlN3)n (n = 2-4) clusters all possess cyclic

structures containing Al–Nα–Al linkages. The relationships between the geometrical parameters and the

oligomerization degree n are discussed. The gas-phase structures of the trimers prefer to exist in the boat-

twisting conformation. As for the tetramer, the most stable isomers have the S4 symmetry structure. The IR

spectra are obtained and assigned by the vibrational analysis. The thermodynamic properties are linearly

related with the oligomerization degree n as well as with the temperature. Meanwhile, the thermodynamic

analysis of the gas-phase reaction suggests that the oligomerization be exothermic and favorable under high

temperature.

Keywords: (Br2AlN3)n (n = 1-4) clusters, density functional theory (DFT), structural feature, IR spectra,

thermodynamic properties.

INTRODUCTION

Aluminum nitrides (AlN) have attracted increasing interest for microelectronics and optoelectronics due to their

excellent material properties such as a wide band gap, low electrical and high thermal conductivity, high melting temperature, hardness, and good chemical stability [1-3]. The most successful approach to AlN involves the reaction of trimethylaluminum (AlMe3) with ammonia (NH3) at a temperature in excess of 1050°C [4]. However, such elevated growth temperatures may lead to unintentional nitrogen vacancies limiting the p-doping capability. Alternative synthetic routes to stoichiometric AlN materials involve the use of single-source precursors containing strong Al-N bonds in the hope of lowering the reaction temperature [5]. Other possible advantages include the elimination of the inefficient use of ammonia, the minimization of parasitic pre-reactions in the gas phase, and the simplification of the processes.

Because the azide group seems to be the optimal build-in nitrogen source and nitrides were successfully deposited

without additional nitrogen sources, particularly promising are single-source precursors that contain the azide (N3) ligand as the nitrogen source [6-18]. The product formed has a high degree of carbon contamination due to pyrolysis of the organic substituent. So, McMurran et al. reported several related routes for the GaN synthesis utilizing a new class of inorganic azide compounds that incorporate hydrogen and halide ligands [14-18] instead of organic groups. However, the inorganic metal azide clusters of aluminum have seemingly been the subject of little experimental studies [19].

The reasons are the difficulties arising in the experimental detection. Reliable structures, IR spectra, and thermodynamic properties of many gas-phase precursors are not at all well-documented, and theoretical predictions for the School of Chemistry and Chemical Engineering, Linyi University, Linyi 276005, P. R. China; xiaqiying@163.com.

The text was submitted by the authors in English. Zhurnal Strukturnoi Khimii, Vol. 54, No. 1, pp. 40-47, January-February, 2013. Original article submitted September 12, 2011.

32 0022-4766/13/5401-0032