Low-energy atomic displacement model of SRIM simulations

Radiation-induced atomic displacement damage is a pressing issue for materials.The present work investigates the number of atomic displacements using the Primary Knock-on Atom (PKA) energy E_(PKA)and threshold displacement energy E_(d)as two major parameters via lowenergy SRIM Binary Collision Approximation (BCA) full cascade simulations.It is found that the number of atomic displacements cannot be uniquely determined by E_(PKA)/E_(d )or E_(D) /E_(d)(E_(D) refers to the damage energy) when the energy is comparable with E_(d).The effective energy E_(D,eff)proposed in the present work allows to describing the number of atomic displacements for most presently studied monatomic materials by the unique variable E_(D,eff)/E_(d).Nevertheless,it is noteworthy that the BCA simulation damage energy depends on E_(d),whereas the currently used analytical method is independent of E_(d).A more accurate analytical damage energy function should be determined by including the dependence on E_(d).

Structural and Magnetic Property of Ion Irradiated TiO2 Single Crystals

Ferromagnetism is induced in pure TiO2 single crystals by oxygen ion irradiation. The ferro- magnetism is observed up to room temperature and is with weak temperature dependence. By combining X-ray diffraction, Rutherford backseattering/channelling, Raman scattering, and electron-spin resonance spectroscopy, supperconducting quantum interference device, displacement per atom, we measured tile lattice damage accumulation with increasing flu- ences. A defect complex, i.e., Ti3＋ on the substitutional accoiflpanied by oxygen vacancies, has been identified in the irradiated Ti02. This kind of defect complex results in a local （TiO6-x） stretching Raman mode. We elucidate that Ti3＋ with one unpaired 3d electron provide the local magnetic moments.

Dislocation-mediated migration of interphase boundaries

Faceted interphase boundaries(IPBs)are commonly observed in lath-shaped precipitates in alloys consisting of simple face-centred cubic(fcc),body centred-cubic(bcc)or hexagonal closed packed(hcp)phases,which normally contain one or two sets of parallel dislocations.The influence of these dislocations on interface migration and possible accompanying long-range strain field remain unclear.To elucidate this,we carried out atomistic simulations to investigate the dislocation-mediated migration processes of IPBs in a pure-iron system.Our results show that the migration of these IPBs is accompanied with the slip of interfacial dislocations,even in high-index slip planes,with two migration modes were observed:the first mode is the uniform migration mode that occurs only when all of the dislocations slip in a common slip plane.A shear-coupled interface migration was observed for this mode.The other interfaces propagate in the stick-slip migration mode that occurs when the dislocations glide on different slip planes,involving dislocation reaction or tangling.A quantitative relationship was established to link the atomic displacements with the dislocation structure,slip plane,and interface normal.The macroscopic shear deformation due to the effect of overall atomic displacement shows a good agreement with the results obtained based on the phenomenological theory of martensite crystallography.Our findings have general implications for the understanding of phase transformations and the surface relief effect at the atomic scale.