local lattice
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Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1419
Author(s):  
Shinobu Aoyagi ◽  
Ayumi Aoyagi ◽  
Hiroaki Takeda ◽  
Hitoshi Osawa ◽  
Kazushi Sumitani ◽  
...  

Lead-containing relaxor ferroelectrics show enormous piezoelectric capabilities relating to their heterogeneous structures. Time-resolved nanobeam X-ray diffraction reveals the time and position dependences of the local lattice strain on a relaxor ferroelectric single crystal mechanically vibrating and alternately switching, as well as its polarization under an alternating electric field. The complicated time and position dependences of the Bragg intensity distributions under an alternating electric field demonstrate that nanodomains with the various lattice constants and orientations exhibiting different electric field responses exist in the measured local area, as the translation symmetry breaks to the microscale. The dynamic motion of nanodomains in the heterogeneous structure, with widely distributed local lattice strain, enables enormous piezoelectric lattice strain and fatigue-free ferroelectric polarization switching.


Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Tianxin Wang ◽  
Xiaoyi Xu ◽  
Lei Yang ◽  
Shuo Yan ◽  
Xueli Hu ◽  
...  

Abstract We propose and experimentally demonstrate a laser-writing-induced selective chemical etching (LWISCE) technique for effective micro-fabrication of lithium niobate (LN) crystal. Laser writing of LN crystal produces negative domains and domain walls. Also, it causes local lattice defects, in which the etching rates are significantly increased in comparison to the original LN crystal. In experiment, we use the LWISCE technique to fabricate various fork gratings in an X-cut LN crystal for the generation of vortex beams. In comparison to etching an untreated X-cut LN crystal, the etching rates of the laser-writing-induced boundaries and the central laser-irradiated areas are enhanced by a factor of 26 and 16, respectively. The width and depth of fork grating structure can be precisely controlled by laser writing parameters. Our method provides an efficient mask-free micro-fabrication technique for LN crystal, which can be readily applied to other ferroelectric crystals such as lithium tantalate, potassium titanyl phosphate and barium calcium titanate.


2021 ◽  
Vol 203 ◽  
pp. 114104
Author(s):  
Fanchao Meng ◽  
Wenyan Zhang ◽  
Zhukun Zhou ◽  
Ruixin Sheng ◽  
Andrew C.-P. Chuang ◽  
...  

2021 ◽  
Vol 11 (19) ◽  
pp. 9054
Author(s):  
Thu Nhi Tran Caliste ◽  
Alexis Drouin ◽  
Damien Caliste ◽  
Carsten Detlefs ◽  
José Baruchel

We observe a long-range distortion field between parallel dislocations with opposite Burgers vectors in a platelet-shaped single crystal of 4H-SiC with a low dislocation density (~103 cm/cm3). This distortion field is in the µradian range when the distance D between dislocations is in the ~50–250 µm range. We were able to characterise this weak distortion field through Rocking Curve Imaging (RCI), a highly sensitive Bragg diffraction imaging technique using monochromatic synchrotron radiation. From the experimental images, we generate maps of the angle of maximum reflectance (“peak position”) that provide a measurement of the local lattice orientation. Deviations from the crystal matrix orientation are associated with the long-range distortion field around dislocations. Between parallel dislocations with opposite Burgers vectors, this distortion does not decay to zero but towards a constant value α. We propose a simple model considering the angular parameter α characterising the distortion. This model indicates that α should roughly vary as 1/D. This appears to be in fair agreement with our experimental data.


Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1399
Author(s):  
Huijuan Ge ◽  
Chengfeng Cui ◽  
Hongquan Song ◽  
Fuyang Tian

Using the ab initio calculations, we study the lattice distortion of HfNbTaTiVC5, HfNbTaTiZrC5 and MoNbTaTiVC5 high-entropy carbide (HEC) ceramics. Results indicate that the Bader atomic radius and charge transfer in HECs is very close to those from binary carbide. The degree of lattice distortion strongly depends on the alloying element. The Bader atomic radius can excellently describe the lattice distortion in HEC. Further, the corresponding atomic radius and formation enthalpy of binary carbides may be indicators to predict the single-phase HECs.


2021 ◽  
Vol 54 (4) ◽  
Author(s):  
Hongyu Peng ◽  
Tuerxun Ailihumaer ◽  
Yafei Liu ◽  
Balaji Raghotharmachar ◽  
Xianrong Huang ◽  
...  

The contrast of dislocations in 4H-SiC crystals shows distinctive features on grazing-incidence X-ray topographs for diffraction at different positions on the operative rocking curve. Ray-tracing simulations have previously been successfully applied to describe the dislocation contrast at the peak of a rocking curve.The present work shows that the dislocation images observed under weak diffraction conditions can also be simulated using the ray-tracing method. These simulations indicate that the contrast of the dislocations is dominated by orientation contrast. Analysis of the effective misorientation reveals that the dislocation contrast in weak-beam topography is more sensitive to the local lattice distortion, consequently enabling information to be obtained on the dislocation sense which cannot be obtained from the peak.


Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 873
Author(s):  
Marco Coco ◽  
Giovanni Mascali ◽  
Vittorio Romano

The definition of temperature in non-equilibrium situations is among the most controversial questions in thermodynamics and statistical physics. In this paper, by considering two numerical experiments simulating charge and phonon transport in graphene, two different definitions of local lattice temperature are investigated: one based on the properties of the phonon–phonon collision operator, and the other based on energy Lagrange multipliers. The results indicate that the first one can be interpreted as a measure of how fast the system is trying to approach the local equilibrium, while the second one as the local equilibrium lattice temperature. We also provide the explicit expression of the macroscopic entropy density for the system of phonons, by which we theoretically explain the approach of the system toward equilibrium and characterize the nature of the equilibria, in the spatially homogeneous case.


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