  We investigate the scaling properties of the two-dimensional (2D) Anderson
model of localization with purely off-diagonal disorder (random hopping). Using
the transfer-matrix method and finite-size scaling we compute the infinite-size
localization lengths for bipartite square and hexagonal 2D lattices,
non-bipartite triangular lattices and different distribution functions for the
hopping elements. We show that for small energies the localization lengths in
the bipartite case diverge with a power-law behavior. The corresponding
exponents are in the range $0.2 - 0.6$ and seem to depend on the type and the
strength of disorder.
