The geometrical, electronic and vibrational properties of pure (Al2O3)(n) (n = 9, 10, 12, 15) clusters and Ni-doped (Al2O3)(9-10) clusters are investigated by density functional theory. There are four different Ni-doped (Al2O3)(9) clusters and one Ni-doped (Al2O3)(10) cluster taken into account. Compared with the pure clusters, the Ni-doped (Al2O3)(9-10) clusters have narrower HOMO-LUMO energy gaps. The results indicate that the impurity of Ni atom is mainly responsible for the reduction of the HOMO-LUMO energy gap. One characteristic vibration band at about 1030 cm(-1) is found in the vibrational frequencies of the Ni-doped (Al2O3)(9-10) clusters, which is caused by the asymmetric Al-O-Al stretching vibration. Another band at around 826 cm(-1) involving the characteristic vibration of Ni-O bond is in good agreement with experimental results. (C) 2011 Elsevier B.V. All rights reserved.