Oyeon Kum^a, Young Han Shin^b and Eok-Kyun Lee^b

^a Agency for Defense Development, P. O. Box 35, Yuseongku, Taejon, Korea
^b Korea Advanced Institute of Science and Technology 373-1 Gusongdong, Yuseongku, Taejon, Korea

We develop a molecular dynamic method to evaluate the full Lyapunov spectrum for two-dimensonal fluids composed of rigid diatomic molecules. The Lyapunov spectra are obtained for 18 rigid diatomic molecules for various bond lengths d(10-3 <~ d <~ 1.0) in two dimensions with periodic boundary conditions, and interacting with Hoover and Weeks-Chandler-Anderson short-range repulsive forces. The general trends and characteristic features of the Lyapunov spectra are examined for both potentials. Our results are compared with those obtained from I. Borzsak et al. [Phys. Rev. E 53, 3694 (1996)], whose model uses the Lagrange multiplier method.