After several initial geometric configurations are relaxed, a ring structure of Ga8As8 cluster is found by first-principles calculations. It is shown that GaAs bond lengths are somewhat longer or shorter than that in bulk GaAs. The calculated vibrational spectrum implies that the optimized geometry is located at the minimum point of the potential surface. There are only two strong peaks of IR absorption, one is at about 260 cm(-1) and another is at 349 cm(-1). The vibrations of Ga-As bonds in plane of ring are the primary IR vibration at about 349 cm(-1). Raman spectrum shows that the vibrations of two layers of the GaAs ring are the primary Raman vibration at about 222 cm(-1). The dipole polarizability anisotropy invariant and hyperpolarizability also are discussed. (C) 2003 Elsevier B.V. All rights reserved.