The method of computer modeling investigates the mechanism of destruction BCC lattice of silver at deformation of shift (111)<121> and the direction of unstable displacement of atoms in a crystal is determined at infringement of a dynamic condition of stability. The most dangerous direction of movement of atoms in a crystal, resulting to structural instability is shown, that, not completely coincides with a direction <121> laying in a plane (111), and has a perpendicular component in a direction [111].

Keywords: FCC lattice, mechanism of destruction, direction of unstable displacement, structural instability, phonon spectra, wave vector.