C. Seko et K. Takatsuka, ORIGIN OF THE COMPLEX DYNAMICS IN STRUCTURAL ISOMERIZATION OF SMALL CLUSTERS - THE EFFECTS OF POTENTIAL TOPOGRAPHY, The Journal of chemical physics, 109(12), 1998, pp. 4768-4781
The dependence of Lifetime distribution in isomerization dynamics of A
r-7-like clusters on the potential topography is reported. Using the s
caled Morse potential V=Sigma(i<j)(e(-2(rho ij-rho 0)) -2e(-(rho ij-rh
o 0))), where rho(ij) is an internuclear distance, and rho(0), the equ
ilibrium distance of the isolated diatomic molecule, is the only indep
endent parameter that uniquely specifies the system Hamiltonian, we ha
ve examined the dynamics for two typical values of rho(0). In the high
enough energy region, which is called the liquidlike phase, the clust
er of a small po (called a compact cluster) has an exponential form fo
r the lifetime distribution. In contrast, dynamics on the potential wi
th a large po (a loose cluster) exhibits a large deviation from the ex
ponential form, its mixing dynamics notwithstanding; it displays a lar
ge hole in the short lifetime region and a steep clifflike structure i
n the even shorter lifetime region embedded in the hole. Since the dev
iation is so clear, the present system offers an excellent example wit
h which to investigate the dependence of phase space structure on the
potential topography. We have identified the mechanisms of formation b
oth of the hole and cliff. The hole is particularly important to under
stand how mixing dynamics can deviate from the statistically simple ex
ponential distribution. By comparing a variety of quantities that char
acterize the system dynamics, we propose a conceptual picture to under
stand the basic difference between the dynamics on compact and loose p
otentials, in which the complexity of the dynamics is ascribed to the
bifurcation of the reaction tubes and to the turning-point distributio
ns clinging to the branching places of such bifurcated tubes. (C) 1998
American Institute of Physics.