
A model, dubbed the inverse Kröner model, is proposed to calculate the diffraction elastic constants from the elastic constants of a single crystal. It is related to the classic Kröner model, and both are identified as bounds on the diffraction elastic constants. Through the grain shape as controlling parameter, the classic Kröner model is bound by the hkl-independent mechanical limit given by the bulk elastic constants of the matrix, while the inverse Kröner model approaches the Reuss limit.