Narrow Results

Field-ion microscopy and molecular dynamics simulation were used for the characterization of the translation states at special grain boundaries in tungsten. It is revealed that rigid-body displacement had the component of displacement parallel to the [110] direction equal to 0 or 1 interplanar spacing. Full vectors of lateral shifts are described by broad statistical distribution. The mathematical simulation revealed two mirror-symmetry-breaking lateral translations along the direction of the Σ9 grain boundary corresponding to different atomic structures. It is shown that the partial disconnection with the Burgers vector can be considered as the elemental carriers of grain-boundary polymorphic transformation.

The interaction of accelerated helium atoms with the atomic-smooth surface of tun+gsten single crystals was investigated using the low-temperature field-ion microscope, equipped with the source of helium atoms with an energy of 5 keV together with the techniques of molecular dynamics. It was observed the effect of the surface channeling of fast atoms of a target along the surface steps which occurs as a result of the collision cascade induced by the incident projectile. A substantial part of these displaced atoms in the target gains momentum oriented along the < 111 > close-packed crystallographic directions. The fine morphology of the trajectory of an excited tungsten atom reveals the transverse oscillations of the W atom normally to the < 111 > surface atomic step. The rate of the kinetic energy loss during the surface channeling of fast tungsten atoms does not exceed 0.4 eV/Å. This provides relatively large displaced surface atom ranges along the close-packed atomic steps. The found out results can be regarded as a special case of the correlation mechanism of the radiation-induced surface mass transfer.