  The collective modes of two-dimensional ordered atomic arrays can modify the
radiative environment of embedded atomic impurities. We analyze the role of the
lattice geometry on the impurity's emission linewidth by comparing the
effective impurity decay rate obtained for all non-centered Bravais lattices
and an additional honeycomb lattice. We demonstrate that the lattice geometry
plays a crucial role in determining the effective decay rate for the impurity.
In particular, we find that the minimal effective decay rate appears in
lattices where the number of the impurity's nearest neighbours is maximal and
the number of distinct distances among nearest neighbours is minimal. We
further show that, in the choice between interstitial and substitutional
placement of the impurity, the former always wins by exhibiting a lower decay
rate and longer photon storage. For interstitial placements, we determine the
optimal impurity position in the lattice plane, which is not necessarily found
in the center of the lattice plaquette.
