Experimental observation of TiN(12) (+) cluster and theoretical investigation of its stable and metastable isomers

TiN(n) (+) clusters were generated by laser ablation and analyzed experimentally by mass spectrometry. The results showed that the mass peak of the TiN(12) (+) cluster is dominant in the spectrum. The TiN(12) (+) cluster was further investigated by photodissociation experiments with 266, 532 and 1064 nm photons. Density functional calculations were conducted to investigate stable structures of TiN(12) (+) and the corresponding neutral cluster, TiN(12). The theoretical calculations found that the most stable structure of TiN(12) (+) is Ti(N(2))(6) (+) with O (h) symmetry. The calculated binding energy is in good agreement with that obtained from the photodissociation experiments. The most stable structure of neutral TiN(12) is Ti(N(2))(6) with D (3d) symmetry. The Ti–N bond strengths are greater than 0.94 eV in both Ti(N(2))(6) (+) and its neutral counterpart. The interaction between Ti and N(2) weakens the N–N bond significantly. For neutral TiN(12), the Ti(N(3))(4) azide, the N(5)TiN(7) sandwich structure and the N(6)TiN(6) structure are much higher in energy than the Ti(N(2))(6) complex. The DFT calculations predicted that the decomposition of Ti(N(3))(4), N(5)TiN(7), and N(6)TiN(6) into a Ti atom and six N(2) molecules can release energies of about 139, 857, and 978 kJ mol(–1) respectively.