scholarly journals Rotational transition, domain formation, dislocations, and defects in vortex systems with combined sixfold and twelvefold anisotropic interactions

2020 ◽  
Vol 101 (22) ◽  
Author(s):  
M. W. Olszewski ◽  
M. R. Eskildsen ◽  
C. Reichhardt ◽  
C. J. O. Reichhardt
2018 ◽  
Vol 20 (2) ◽  
pp. 023005 ◽  
Author(s):  
M W Olszewski ◽  
M R Eskildsen ◽  
C Reichhardt ◽  
C J O Reichhardt

Author(s):  
Joseph J. Comer

Domains visible by transmission electron microscopy, believed to be Dauphiné inversion twins, were found in some specimens of synthetic quartz heated to 680°C and cooled to room temperature. With the electron beam close to parallel to the [0001] direction the domain boundaries appeared as straight lines normal to <100> and <410> or <510> directions. In the selected area diffraction mode, a shift of the Kikuchi lines was observed when the electron beam was made to traverse the specimen across a boundary. This shift indicates a change in orientation which accounts for the visibility of the domain by diffraction contrast when the specimen is tilted. Upon exposure to a 100 KV electron beam with a flux of 5x 1018 electrons/cm2sec the boundaries are rapidly decorated by radiation damage centers appearing as black spots. Similar crystallographio boundaries were sometimes found in unannealed (0001) quartz damaged by electrons.


2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Lingli Huang ◽  
Fangyuan Zheng ◽  
Honglin Chen ◽  
Quoc Huy Thi ◽  
Xin Chen ◽  
...  

AbstractMartensite is a needle-shaped microstructure formed by a rapid, diffusionless transformation and significantly affects the mechanical properties of materials. Here, in two-dimensional ReS2 we show that martensite-like domain structures can form via a diffusionless transformation, involving small lattice deformations. By analyzing the strain distribution and topology of the as-grown chemical vapor deposition samples, we find that cooling-induced strain at the ReS2/substrate interface is responsible for the mechanical loading and is essential for martensite-like domain formation. Meanwhile, the effect of cooling rate, flake size and substrate on the microstructures revealed the mechanical origin of the transformation. The strain-induced lattice reconstructions are rationalized and possibly lead to ferroelastic effects. In view of the strong anisotropy in electronic and optical properties in two dimensional materials like ReS2, opportunities exist for strain-correlated micro/nanostructure engineering, which has potential use in next-generation strain-tunable devices.


1973 ◽  
Vol 24 (2) ◽  
pp. 120-128 ◽  
Author(s):  
J E Barsby

SummarySolutions to the problem of separated flow past slender delta wings for moderate values of a suitably defined incidence parameter have been calculated by Smith, using a vortex sheet model. By increasing the accuracy of the finite-difference technique, and by replacing Smith’s original nested iteration procedure, to solve the non-linear simultaneous equations that arise, by a Newton’s method, it is possible to extend the range of the incidence parameter over which solutions can be obtained. Furthermore for sufficiently small values of the incidence parameter, new and unexpected results in the form of vortex systems that originate inboard from the leading edge have been discovered. These new solutions are the only solutions, to the author’s knowledge, of a vortex sheet leaving a smooth surface.Interest has centred upon the shape of the finite vortex sheet, the position of the isolated vortex, and the lift, and variations of these quantities are shown as functions of the incidence parameter. Although no experimental evidence is available, comparisons are made with the simpler Brown and Michael model in which all the vorticity is assumed to be concentrated onto an isolated line vortex. Agreement between these two models becomes very close as the value of the incidence parameter is reduced.


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