  LiCrO2 is a 2D triangular antiferromagnet, isostructural with the common
battery material LiCoO2 and a well-known Jahn-Teller antiferromagnet NaNiO2. As
opposed to the latter, LiCrO2 exibits antiferromagnetic exchange in Cr planes,
which has been ascribed to direct Cr-Cr d-d overlap. Using LDA and LDA+U first
principles calculations I confirm this conjecture and show that (a) direct d-d
overlap is indeed enhanced compared to isostructural Ni and Cr compounds, (b)
p-d charge transfer gap is also enhanced, thus suppressing the ferromagnetic
superexchange, (c) the calculated magnetic Hamiltonian maps well onto the
nearest neighbors Heisenberg exchange model and (d) interplanar inteaction is
antiferromagnetic.
