查看更多>>摘要：Point defects and their clusters generated through irradiation can have significant impact on the physical and mechanical properties of materials. However, direct experimental visualization of these small-scale defects using high-resolution scanning transmission electron microscopy remains a challenging task. Here, using thorium dioxide (ThO2) with the fluorite structure as a model system, we demonstrate the use of ab initio basin-hopping simulations in synergy with object kinetic Monte Carlo simulations as a powerful tool for identifying small defect complexes in irradiated materials. In addition to providing quantitative insights into defect evolution in ThO2 under irradiation, our study reveals an unexpected role of bound anti-Schottky defect clusters in mediating defect transport. Remarkably, despite their poor thermal stability against dissociation at high temperatures, the transient formation of bound anti-Schottky defects under irradiation and their subsequent migration provide the dominant mechanism for the growth of large interstitial loops that have been experimentally observed in ThO2.
查看更多>>摘要：The ultrafast ferroelectric polarization dynamics excited by intense THz pulses (with an electric field up to 23 MV/cm) in a multidomain Ba(0.8)Sr(0.2)TiO(3 & nbsp;)thin film has been experimentally demonstrated using optical second harmonic generation (SHG) probe. The obtained nonlinear dependence of the SHG intensity on the electric field of the THz pulse can be explained in terms of Landau-Khalatnikov equation by a transient ferroelectric polarization reversal. The best agreement between the experimental and simulated data was obtained when taking into account the multidomain structure of the film and carrying out convolution of the simulated polarization dynamics and the optical probe pulse.
Yildirim, C.Mavrikakis, N.Cook, P. K.Rodriguez-Lamas, R....
7页
查看更多>>摘要：We present a multiscale study on the recovery and recrystallisation of a heavily deformed (85% reduction in size) Fe-Si-Sn alloy using a combination of dark field X-ray microscopy (DFXM), synchrotron X-ray diffraction (SXRD) and electron backscatter diffraction (EBSD). By utilizing DFXM, we focus on a grain within the high stored energy (HSE) regions, and track it through consecutive isothermal annealing steps. The intra-granular structure of the as-deformed grain reveals deformation bands separated by asymptotic to 3-5C; misorientation. During the early stages of annealing, cells with 2-5C; misorientation form while new nuclei appear. The recrystallized grains nucleate near prior grain boundaries, having a typical internal angular spread of < 0.05C;. The SXRD results suggest no significant macroscopic texture change after annealing for 1400s at 610 & nbsp;C in the HSE regions. All results indicate that higher misorientation zones such as grain boundaries or junction points of deformation bands are preferential nucleation regions.
NSTL
Elsevier