  The ground state phase transitions in the distorted S=1 kagome Heisenberg
antiferromagnet (KHAF) with single-site anisotropy D are studied by the
numerical exact diagonalization method. For strong easy plane anisotropy, the
hexgonal singlet solid (HSS) ground state of the uniform KHAF is destroyed and
large-D state is realized. The quantum phase transition between these two
states is analogous to the Haldane-large-D transition in the S=1
antiferromagnetic Heisenberg chain. The combined effect of the sqrt(3) times
sqrt(3) lattice distortion and single site anisotropy is also investigated. The
ground state phase diagram expected from the numerical results is presented.
The presence of this transition is consistent with the HSS picture of the
ground state of the uniform S=1 KHAF and supports its validity.
