  The dynamics of the one-dimensional spin-1/2 quantum XXZ model with random
fields is investigated by the recurrence relations method. When the fields
satisfy the bimodal distribution, the system shows a crossover between a
collective-mode behavior and a central-peak one with increasing field while the
anisotropy parameter {\Delta} is small; a disordered behavior replaces the
crossover as {\Delta} increases. For the cases of Gaussian and double-Gaussian
distributions, when the standard deviation is small, the results are similar to
that of the bimodal distribution; while the standard deviation is large enough,
the system only shows a disordered behavior regardless of {\Delta}.
