Experimental and theoretical investigation of three-dimensional nitrogen-doped aluminum clusters Al8N- and Al8N.

The structure and electronic properties of the Al(8)N(-) and Al(8)N clusters were investigated by combined photoelectron spectroscopy and ab initio studies. Congested photoelectron spectra were observed and experimental evidence was obtained for the presence of multiple isomers for Al(8)N(-). Global minimum searches revealed several structures for Al(8)N(-) with close energies. The calculated vertical detachment energies of the two lowest-lying isomers, which are of C(2v) and C(s) symmetry, respectively, were shown to agree well with the experimental data. Unlike the three-dimensional structures of Al(6)N(-) and Al(7)N(-), in which the dopant N atom has a high coordination number of 6, the dopant N atom in the two low-lying isomers of Al(8)N(-) has a lower coordination number of 4 and 5, respectively. The competition between the Al-Al and Al-N interactions are shown to determine the global minimum structures of the doped aluminum clusters and results in the structural diversity for both Al(8)N(-) and Al(8)N.