  In this paper, we establish moderate deviations for the chemical distance in
Bernoulli percolation. The chemical distance between two points is the length
of the shortest open path between these two points. Thus, we study the size of
random fluctuations around the mean value, and also the asymptotic behavior of
this mean value. The estimates we obtain improve our knowledge of the
convergence to the asymptotic shape. Our proofs rely on concentration
inequalities proved by Boucheron, Lugosi and Massart, and also on the
approximation theory of subadditive functions initiated by Alexander.
