Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China
; Wuhan Univ Technol, Sch Nat Sci, Wuhan 430079, Peoples R China
; Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China
The entanglement dynamics of two stretching vibrations in theoretically typical local- and normal-mode molecules and realistic molecules H2O and SO2 in an algebraic model is studied in terms of the reduced-density linear entropy with initial entangled states taken to be two-mode squeezed vacuum states. It is shown that the behaviour of the entropy in theoretically typical molecules appears to be more regular than that in realistic ones, and that the entropy becomes irregular as the amplitude of two-mode squeezed vacuum states increases. For initial states with a small amplitude, it is demonstrated that the periodicity and the "classical" beat phenomenon of the entropy occur with the beat in theoretically typical molecules being more regular than that in realistic molecules H2O and SO2.