Lyapunov instability of rigid diatomic molecules in three dimensions - a simpler method

We present a new method to calculate Lyapunov exponents of rigid diatomic molecules in three dimensions (12N dimensional phase space). The spectra of Lyapunov exponents are obtained for 32 rigid diatomic molecules interacting through the Weeks-Chandler-Anderson(WCA) potential for various bond length and densities, and compared with those in Y.-H. Shin et al. [Phys. Rev. E 64, 041106 (2001)]. Our algorithm is easy to implement and total CPU time is relatively inexpensive.