  The full-potential linearized augmented plane wave (FP-LAPW) method with the
generalized gradient approximation (GGA) for the exchange-correlation potential
has been applied to predict the elastic properties of quaternary oxyarsenide
LaOFeAs - the basic phase for the newly discovered 26-52K superconductors. The
optimized lattice parameters, independent elastic constants (Cij), bulk modulus
B, compressibility betta, and shear modulus G are evaluated and discussed. For
the first time the numerical estimates of the elastic parameters for
polycrystalline LaOFeAs ceramics are performed. Our analysis shows that LaOFeAs
belong to the anisotropic mechanically stable systems; a parameter limiting the
mechanical stability of this material is the shear modulus. In addition,
LaOFeAs is a soft material (B -98 GPa) with high compressibility (betta -
0.0102 1/GPa); lays at the border of a brittle behavior and adopts a high ionic
contribution in intra-atomic bonding.
