  It is widely accepted that the low-energy physics in edge-sharing cuprate
materials has one-dimensional (1D) character. The relevant model to study such
systems is believed to be the 1D extended Heisenberg model with ferromagnetic
nearest-neighbor (NN) interaction and antiferromagnetic next-nearest-neighbor
one. Thus far, however, theoretical studies of such materials have been
confined to the case of isotropic interactions. In the present work, we compare
the spin susceptibility of the 1D extended Heisenberg model with anisotropy in
the NN channel, obtained by means of the Transfer Matrix Renormalization Group
method, with that of the edge-sharing chain cuprate Li$_2$CuO$_2$.
