  Rapidity/seudorapidity densities for charged particles and their centrality,
rapidity and energy dependence in Au+Au collisions at RHIC are studied in a
quark combination model. Using a Gaussian-type rapidity distribution for
constituent quarks as a result of Landau hydrodynamic evolution, the data at
$\sqrt{s_{NN}}=130, 200$ GeV at various centralities in full pseudorapidity
range are well described, and the charged particle multiplicity are reproduced
as functions of the number of participants. The energy dependence of the shape
of the $dN_{ch}/d\eta$ distribution is also described at various collision
energies $\sqrt{s_{NN}}=200, 130, 62.4$ GeV in central collisions with same
value of parameters except 19.6 GeV. The calculated rapidity distributions and
yields for the charged pions and kaons in central Au+Au collisions at
$\sqrt{s_{NN}}=200$ GeV are compared with experimental data of the BRAHMS
Collaboration.
