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Tsutomu Ishimasa - One of the best experts on this subject based on the ideXlab platform.
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discovery of superconductivity in Quasicrystal
Nature Communications, 2018Co-Authors: Tsutomu Ishimasa, Kazuhiko Deguchi, K Kamiya, Tsunehiro Takeuchi, Noriyuki Kabeya, N Wada, Akira Ochiai, Keiichiro Imura, Noriaki K SatoAbstract:Superconductivity is ubiquitous as evidenced by the observation in many crystals including carrier-doped oxides and diamond. Amorphous solids are no exception. However, it remains to be discovered in Quasicrystals, in which atoms are ordered over long distances but not in a periodically repeating arrangement. Here we report electrical resistivity, magnetization, and specific-heat measurements of Al–Zn–Mg Quasicrystal, presenting convincing evidence for the emergence of bulk superconductivity at a very low transition temperature of $$T_{\rm c} \cong 0.05$$ K. We also find superconductivity in its approximant crystals, structures that are periodic, but that are very similar to Quasicrystals. These observations demonstrate that the effective interaction between electrons remains attractive under variation of the atomic arrangement from periodic to quasiperiodic one. The discovery of the superconducting Quasicrystal, in which the fractal geometry interplays with superconductivity, opens the door to a new type of superconductivity, fractal superconductivity. Superconductivity is evidenced in crystals and amorphous solids, but remains to be discovered in Quasicrystals. Here, Kamiya et al. report the emergence of bulk superconductivity in Al-Zn-Mg Quasicrystal at a very low transition temperature about 0.05 K.
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phason space analysis and structure modelling of 100 a scale dodecagonal Quasicrystal in mn based alloy
Philosophical Magazine, 2015Co-Authors: Tsutomu Ishimasa, Shuhei Iwami, Norihito Sakaguchi, Ryo Oota, M MihalkovicAbstract:The dodecagonal Quasicrystal classified into the five-dimensional space group P126/mmc, recently discovered in a Mn–Cr–Ni–Si alloy, has been analysed using atomic-resolution spherical aberration-corrected electron microscopy, i.e. high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and conventional transmission electron microscopy. By observing along the 12-fold axis, non-periodic tiling consisting of an equilateral triangle and a square has been revealed, of which common edge length is a = 4.560 A. These tiles tend to form a network of dodecagons of which size is a ≈ 17 A in diameter. The tiling was interpreted as an aggregate of 100 A-scale oriented domains of high- and low-quality Quasicrystals with small crystallites appearing at their boundaries. The Quasicrystal domains exhibited a densely filled circular acceptance region in the phason space. This is the first observation of the acceptance region in an actual dodecagonal Quasicrystal. Atomic structure model consiste...
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quantum critical state in a magnetic Quasicrystal
arXiv: Strongly Correlated Electrons, 2012Co-Authors: Kazuhiko Deguchi, Hiroyuki Takakura, Shuya Matsukawa, N Sato, Taisuke Hattori, Kenji Ishida, Tsutomu IshimasaAbstract:Quasicrystals are metallic alloys that possess long-range, aperiodic structures with diffraction symmetries forbidden to conventional crystals. Since the discovery of Quasicrystals by Schechtman et al. at 1984 (ref. 1), there has been considerable progress in resolving their geometric structure. For example, it is well known that the golden ratio of mathematics and art occurs over and over again in their crystal structure. However, the characteristic properties of the electronic states - whether they are extended as in periodic crystals or localized as in amorphous materials - are still unresolved. Here we report the first observation of quantum (T = 0) critical phenomena of the Au-Al-Yb Quasicrystal - the magnetic susceptibility and the electronic specific heat coefficient arising from strongly correlated 4f electrons of the Yb atoms diverge as T -> 0. Furthermore, we observe that this quantum critical phenomenon is robust against hydrostatic pressure. By contrast, there is no such divergence in a crystalline approximant, a phase whose composition is close to that of the Quasicrystal and whose unit cell has atomic decorations (that is, icosahedral clusters of atoms) that look like the Quasicrystal. These results clearly indicate that the quantum criticality is associated with the unique electronic state of the Quasicrystal, that is, a spatially confined critical state. Finally we discuss the possibility that there is a general law underlying the conventional crystals and the Quasicrystals.
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icosahedral Quasicrystal and 1 1 cubic approximant in au al yb alloys
Philosophical Magazine, 2011Co-Authors: Tsutomu Ishimasa, Yukinori Tanaka, Shiro KashimotoAbstract:A P-type icosahedral Quasicrystal is formed in an Au–Al–Yb alloy with a six-dimensional lattice parameter a 6D = 7.448 A. The composition of the Quasicrystal was analyzed to be Au51Al34Yb15. The Quasicrystal is formed in as-cast alloys and is regarded as metastable with decomposition to other crystalline phases during annealing at 700°C. Among Tsai-type Quasicrystals, this Quasicrystal is situated just between the Zn–Sc group with a smaller a 6D and the larger Cd–Yb group. The intermediate valence of Yb recently observed in this Quasicrystal may be due to this unique situation, namely a smaller major component in Au-Al-Yb than in Cd–Yb. The predominant phase in the annealed specimen is a 1/1 cubic approximant with lattice parameter a = 14.500 A belonging to the space group Im . This phase is stable at the composition Au51Al35Yb14 at 700°C. Rietveld structural analysis indicated that the crystal structure is a periodic arrangement of Tsai-type clusters with four Au–Al atoms at their centers. Chemical order...
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icosahedral Quasicrystal and 1 1 cubic approximant in au al yb alloys
arXiv: Materials Science, 2011Co-Authors: Tsutomu Ishimasa, Yukinori Tanaka, Shiro KashimotoAbstract:A P-type icosahedral Quasicrystal is formed in Au-Al-Yb alloy of which 6-dimensional lattice parameter a6D = 7.448 {\AA}. The composition of the Quasicrystal was analyzed to be Au51Al34Yb15. This Quasicrystal is formed in as-cast alloys, and is regarded as metastable because of decomposition into other crystalline phases by annealing at 700 \degree C. Among Tsai-type Quasicrystals, this Quasicrystal is situated just between Zn-Sc group with smaller a6D and larger Cd-Yb group. Intermediate valence of Yb recently observed in this Quasicrystal may be due to this unique situation, namely smaller major component Au-Al than in Cd-Yb. The predominant phase in the annealed specimen is a 1/1 cubic approximant with lattice parameter a = 14.500 {\AA} belonging to the space group Im-3 . This phase is stable at the composition Au51Al35Yb14 at 700 \degree C. Rietveld structural analysis indicated that the crystal structure is understood as periodic arrangement of Tsai-type clusters each including four Au-Al atoms at their centers. Chemical ordering of Au and Al is characteristics of this approximant.
A.p. Tsai - One of the best experts on this subject based on the ideXlab platform.
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direct observation of growth and stability of al cu fe Quasicrystal thin films
Social Science Research Network, 2019Co-Authors: Hadi Parsamehr, A.p. Tsai, Chunliang Yang, Weiting Liu, Shiwei Chen, Shouyi Chang, Lihjuann Chen, Chihhuang LaiAbstract:Al-Cu-Fe based Quasicrystal thin films exhibit unique surface and mechanical properties. To better understand the formation of the Quasicrystal thin films, we observe direct growth of Quasicrystals, prepared in a multilayer Al-Cu-Fe thin films with subsequent heat treatment, by in-situ synchrotron x-ray diffraction and in-situ transmission electron microscopy during heating and cooling. Using these two methods, we show that the ternary phase is more thermodynamically stable compared to the binary phases at temperature higher than 470 °C during the heating process, and Quasicrystal formation occurs during the cooling process, specifically at 660 °C, after the sample has reached a liquid state. To distinguish Quasicrystal from approximant crystals in the obtained thin film samples, we use high resolution x-ray diffraction to analyze the sample at room temperature. We reveal that the peak broadening increases monotonically along the twofold, threefold, and fivefold high-symmetry directions with the physical scattering vector but does not have systematic dependence on the phason momentum, which suggests that the thin film sample is indeed a Quasicrystal instead of approximant crystals and it is almost free of phason strain. Our study provides a complete understanding of the growth mechanism for thin film Al-Cu-Fe Quasicrystals, which is of particular importance for developing versatile applications of Quasicrystal thin films.
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growth of large single grain Quasicrystals in the ag in yb system by bridgman method
Journal of Crystal Growth, 2009Co-Authors: Can Cui, A.p. TsaiAbstract:Abstract Well-defined single-grain Ag–In–Yb icosahedral Quasicrystals of order of centimeter have been grown by the Bridgman method. The scanning electron microscopy (SEM) observation showed that the compositional distribution in the single-grain Quasicrystals is uniform and Laue X-ray diffraction measurements verified the formation of single-grain icosahedral Quasicrystals. The natural growth direction of the single-grain Quasicrystals is close to a direction parallel to a 2-fold axis. It turns out that the Yb content in the initial melt limited within 15–16 at.% is a critical factor determining the formation of single-grain Quasicrystal. Based on the experimental result, the mechanism of the growth of single-grain Quasicrystal and formation of intermediate zone between Quasicrystal and approximant phases are discussed.
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direct observation of a local thermal vibration anomaly in a Quasicrystal
Nature, 2003Co-Authors: Stephen J Pennycook, Eiji Abe, A.p. TsaiAbstract:Quasicrystals have long-range order with symmetries that are incompatible with periodicity, and are often described with reference to a higher-dimensional analogue of a periodic lattice1,2,3. Within the context of this ‘hyperspace’ crystallography, lattice dynamics of Quasicrystals can be described by a combination of lattice vibrations and atomic fluctuations—phonons and phasons1,4. However, it is difficult to see localized fluctuations in a real-space Quasicrystal structure, and so the nature of phason-related fluctuations and their contribution to thermodynamic stability are still not fully understood. Here we use atomic-resolution annular dark-field scanning transmission electron microscopy to map directly the change in thermal diffuse scattering intensity distribution in the Quasicrystal, through in situ high-temperature observation of decagonal Al72Ni20Co8. We find that, at 1,100 K, a local anomaly of atomic vibrations becomes significant at specific atomic sites in the structure. The distribution of these localized vibrations is not random but well-correlated, with a quasiperiodic length scale of 2 nm. We are able to explain this feature by an anomalous temperature (Debye–Waller) factor for the Al atoms that sit at the phason-related sites defined within the framework of hyperspace crystallography. The present results therefore provide a direct observation of local thermal vibration anomalies in a solid.
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a stable binary Quasicrystal
Nature, 2000Co-Authors: A.p. Tsai, J Q Guo, Eiji Abe, Hiroyuki Takakura, Taku J SatoAbstract:All stable Quasicrystals known so far are composed of at least three metallic elements1,2,3,4. Sixteen years after the discovery of the Quasicrystal5, we describe a stable binary Quasicrystalline alloy in a cadmium–ytterbium (Cd–Yb) system. The structure of this alloy represents a new class of packing of 66-atom icosahedral clusters whose internal structure breaks the icosahedral symmetry. The binary Quasicrystal offers a new opportunity to investigate the relation between thermodynamic stability and quasiperiodic structure, as well as providing a basis for the construction of crystallographic models.
Ashwin J Shahani - One of the best experts on this subject based on the ideXlab platform.
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formation of a single Quasicrystal upon collision of multiple grains
Nature Communications, 2021Co-Authors: Sharon C. Glotzer, Hadi Parsamehr, Insung Han, Kelly L Wang, Andrew T Cadotte, Xianghui Xiao, Ashwin J ShahaniAbstract:Quasicrystals exhibit long-range order but lack translational symmetry. When grown as single crystals, they possess distinctive and unusual properties owing to the absence of grain boundaries. Unfortunately, conventional methods such as bulk crystal growth or thin film deposition only allow us to synthesize either polycrystalline Quasicrystals or Quasicrystals that are at most a few centimeters in size. Here, we reveal through real-time and 3D imaging the formation of a single decagonal Quasicrystal arising from a hard collision between multiple growing Quasicrystals in an Al-Co-Ni liquid. Through corresponding molecular dynamics simulations, we examine the underlying kinetics of Quasicrystal coalescence and investigate the effects of initial misorientation between the growing Quasicrystalline grains on the formation of grain boundaries. At small misorientation, coalescence occurs following rigid rotation that is facilitated by phasons. Our joint experimental-computational discovery paves the way toward fabrication of single, large-scale Quasicrystals for novel applications. Quasicrystals exhibit long-range order without periodicity. The authors report an approach for Quasicrystal fabrication and show through in situ imaging and corresponding simulations the formation of a single decagonal Quasicrystal arising from coalescence of multiple Quasicrystals in a liquid.
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formation of a single Quasicrystal upon collision of multiple grains
arXiv: Materials Science, 2021Co-Authors: Sharon C. Glotzer, Hadi Parsamehr, Insung Han, Kelly L Wang, Andrew T Cadotte, Xianghui Xiao, Ashwin J ShahaniAbstract:Quasicrystals exhibit long-range order but lack translational symmetry. When grown as single crystals, they possess distinctive and unusual properties owing to the absence of grain boundaries. Unfortunately, conventional methods such as bulk crystal growth or thin film deposition only allow us to synthesize either polycrystalline Quasicrystals or Quasicrystals that are at most a few centimeters in size. Here, we reveal through real-time and 3D imaging the formation of a single decagonal Quasicrystal arising from a hard collision between multiple growing Quasicrystals in an Al-Co-Ni liquid. Through corresponding molecular dynamics simulations, we examine the underlying kinetics of Quasicrystal coalescence and investigate the effects of initial misorientation between the growing Quasicrystalline grains on the formation of grain boundaries. At small misorientation, coalescence occurs following rigid rotation that is facilitated by phasons. Our joint experimental-computational discovery paves the way toward fabrication of single, large-scale Quasicrystals for novel applications.
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dynamic observation of dendritic Quasicrystal growth upon laser induced solid state transformation
Physical Review Letters, 2020Co-Authors: Insung Han, Hadi Parsamehr, Joseph T Mckeown, Ling Tang, Caizhuang Wang, M J Kramer, Ashwin J ShahaniAbstract:We report the laser-induced solid-state transformation between a periodic "approximant" and Quasicrystal in the Al-Cr system during rapid quenching. Dynamic transmission electron microscopy allows us to capture in situ the dendritic growth of the metastable Quasicrystals. The formation of dendrites during solid-state transformation is a rare phenomenon, which we attribute to the structural similarity between the two intermetallics. Through ab initio molecular dynamics simulations, we identify the dominant structural motif to be a 13-atom icosahedral cluster transcending the phases of matter.
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probing the growth and melting pathways of a decagonal Quasicrystal in real time
Scientific Reports, 2017Co-Authors: Insung Han, Xianghui Xiao, Ashwin J ShahaniAbstract:How does a Quasicrystal grow? Despite the decades of research that have been dedicated to this area of study, it remains one of the fundamental puzzles in the field of crystal growth. Although there has been no lack of theoretical studies on Quasicrystal growth, there have been very few experimental investigations with which to test their various hypotheses. In particular, evidence of the in situ and three-dimensional (3D) growth of a Quasicrystal from a parent liquid phase is lacking. To fill-in-the-gaps in our understanding of the solidification and melting pathways of Quasicrystals, we performed synchrotron-based X-ray imaging experiments on a decagonal phase with composition of Al-15at%Ni-15at%Co. High-flux X-ray tomography enabled us to observe both growth and melting morphologies of the 3D Quasicrystal at temperature. We determined that there is no time-reversal symmetry upon growth and melting of the decagonal Quasicrystal. While Quasicrystal growth is predominantly dominated by the attachment kinetics of atomic clusters in the liquid phase, melting is instead barrier-less and limited by buoyancy-driven convection. These experimental results provide the much-needed benchmark data that can be used to validate simulations of phase transformations involving this unique phase of matter.
Shiro Kashimoto - One of the best experts on this subject based on the ideXlab platform.
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schottky effect in the i zn ag sc tm icosahedral Quasicrystal and its 1 1 zn sc tm approximant
Physical Review B, 2016Co-Authors: S Jazbec, Shiro Kashimoto, P Koželj, S Vrtnik, Marko Jagodic, Zvonko Jaglicic, J DolinsekAbstract:The analysis of low-temperature specific heat of rare-earth (RE)-containing Quasicrystals and periodic approximants and consequent interpretation of their electronic properties in the $T\ensuremath{\rightarrow}0$ limit is frequently hampered by the Schottky effect, where crystalline electric fields lift the degeneracy of the RE-ion Hund's rule ground state and introduce additional contribution to the specific heat. In this paper we study the low-temperature specific heat of a thulium-containing $i$-Zn-Ag-Sc-Tm icosahedral Quasicrystal and its 1/1 Zn-Sc-Tm approximant, both being classified as ``Schottky'' systems. We have derived the crystal-field Hamiltonian for pentagonal symmetry of the crystalline electric field, pertinent to the class of Tsai-type icosahedral Quasicrystals and their approximants, where the RE ions are located on fivefold axes of the icosahedral atomic cluster. Using the leading term of this Hamiltonian, we have calculated analytically the Schottky specific heat in the presence of an external magnetic field and made comparison to the experimental specific heat of the investigated Quasicrystal and approximant. When the low-temperature specific heat $C$ is analyzed in a $C/T$ versus ${T}^{2}$ scale (as it is customarily done for metallic specimens), the Schottky specific heat yields an upturn in the $T\ensuremath{\rightarrow}0$ limit that cannot be easily distinguished from a similar upturn produced by the electron-electron interactions in exchange-enhanced systems and strongly correlated systems. Our results show that extraction of the electronic properties of RE-containing Quasicrystals from their low-temperature specific heat may be uncertain in the presence of the Schottky effect.
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icosahedral Quasicrystal and 1 1 cubic approximant in au al yb alloys
Philosophical Magazine, 2011Co-Authors: Tsutomu Ishimasa, Yukinori Tanaka, Shiro KashimotoAbstract:A P-type icosahedral Quasicrystal is formed in an Au–Al–Yb alloy with a six-dimensional lattice parameter a 6D = 7.448 A. The composition of the Quasicrystal was analyzed to be Au51Al34Yb15. The Quasicrystal is formed in as-cast alloys and is regarded as metastable with decomposition to other crystalline phases during annealing at 700°C. Among Tsai-type Quasicrystals, this Quasicrystal is situated just between the Zn–Sc group with a smaller a 6D and the larger Cd–Yb group. The intermediate valence of Yb recently observed in this Quasicrystal may be due to this unique situation, namely a smaller major component in Au-Al-Yb than in Cd–Yb. The predominant phase in the annealed specimen is a 1/1 cubic approximant with lattice parameter a = 14.500 A belonging to the space group Im . This phase is stable at the composition Au51Al35Yb14 at 700°C. Rietveld structural analysis indicated that the crystal structure is a periodic arrangement of Tsai-type clusters with four Au–Al atoms at their centers. Chemical order...
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icosahedral Quasicrystal and 1 1 cubic approximant in au al yb alloys
arXiv: Materials Science, 2011Co-Authors: Tsutomu Ishimasa, Yukinori Tanaka, Shiro KashimotoAbstract:A P-type icosahedral Quasicrystal is formed in Au-Al-Yb alloy of which 6-dimensional lattice parameter a6D = 7.448 {\AA}. The composition of the Quasicrystal was analyzed to be Au51Al34Yb15. This Quasicrystal is formed in as-cast alloys, and is regarded as metastable because of decomposition into other crystalline phases by annealing at 700 \degree C. Among Tsai-type Quasicrystals, this Quasicrystal is situated just between Zn-Sc group with smaller a6D and larger Cd-Yb group. Intermediate valence of Yb recently observed in this Quasicrystal may be due to this unique situation, namely smaller major component Au-Al than in Cd-Yb. The predominant phase in the annealed specimen is a 1/1 cubic approximant with lattice parameter a = 14.500 {\AA} belonging to the space group Im-3 . This phase is stable at the composition Au51Al35Yb14 at 700 \degree C. Rietveld structural analysis indicated that the crystal structure is understood as periodic arrangement of Tsai-type clusters each including four Au-Al atoms at their centers. Chemical ordering of Au and Al is characteristics of this approximant.
Insung Han - One of the best experts on this subject based on the ideXlab platform.
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formation of a single Quasicrystal upon collision of multiple grains
Nature Communications, 2021Co-Authors: Sharon C. Glotzer, Hadi Parsamehr, Insung Han, Kelly L Wang, Andrew T Cadotte, Xianghui Xiao, Ashwin J ShahaniAbstract:Quasicrystals exhibit long-range order but lack translational symmetry. When grown as single crystals, they possess distinctive and unusual properties owing to the absence of grain boundaries. Unfortunately, conventional methods such as bulk crystal growth or thin film deposition only allow us to synthesize either polycrystalline Quasicrystals or Quasicrystals that are at most a few centimeters in size. Here, we reveal through real-time and 3D imaging the formation of a single decagonal Quasicrystal arising from a hard collision between multiple growing Quasicrystals in an Al-Co-Ni liquid. Through corresponding molecular dynamics simulations, we examine the underlying kinetics of Quasicrystal coalescence and investigate the effects of initial misorientation between the growing Quasicrystalline grains on the formation of grain boundaries. At small misorientation, coalescence occurs following rigid rotation that is facilitated by phasons. Our joint experimental-computational discovery paves the way toward fabrication of single, large-scale Quasicrystals for novel applications. Quasicrystals exhibit long-range order without periodicity. The authors report an approach for Quasicrystal fabrication and show through in situ imaging and corresponding simulations the formation of a single decagonal Quasicrystal arising from coalescence of multiple Quasicrystals in a liquid.
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formation of a single Quasicrystal upon collision of multiple grains
arXiv: Materials Science, 2021Co-Authors: Sharon C. Glotzer, Hadi Parsamehr, Insung Han, Kelly L Wang, Andrew T Cadotte, Xianghui Xiao, Ashwin J ShahaniAbstract:Quasicrystals exhibit long-range order but lack translational symmetry. When grown as single crystals, they possess distinctive and unusual properties owing to the absence of grain boundaries. Unfortunately, conventional methods such as bulk crystal growth or thin film deposition only allow us to synthesize either polycrystalline Quasicrystals or Quasicrystals that are at most a few centimeters in size. Here, we reveal through real-time and 3D imaging the formation of a single decagonal Quasicrystal arising from a hard collision between multiple growing Quasicrystals in an Al-Co-Ni liquid. Through corresponding molecular dynamics simulations, we examine the underlying kinetics of Quasicrystal coalescence and investigate the effects of initial misorientation between the growing Quasicrystalline grains on the formation of grain boundaries. At small misorientation, coalescence occurs following rigid rotation that is facilitated by phasons. Our joint experimental-computational discovery paves the way toward fabrication of single, large-scale Quasicrystals for novel applications.
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dynamic observation of dendritic Quasicrystal growth upon laser induced solid state transformation
Physical Review Letters, 2020Co-Authors: Insung Han, Hadi Parsamehr, Joseph T Mckeown, Ling Tang, Caizhuang Wang, M J Kramer, Ashwin J ShahaniAbstract:We report the laser-induced solid-state transformation between a periodic "approximant" and Quasicrystal in the Al-Cr system during rapid quenching. Dynamic transmission electron microscopy allows us to capture in situ the dendritic growth of the metastable Quasicrystals. The formation of dendrites during solid-state transformation is a rare phenomenon, which we attribute to the structural similarity between the two intermetallics. Through ab initio molecular dynamics simulations, we identify the dominant structural motif to be a 13-atom icosahedral cluster transcending the phases of matter.
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probing the growth and melting pathways of a decagonal Quasicrystal in real time
Scientific Reports, 2017Co-Authors: Insung Han, Xianghui Xiao, Ashwin J ShahaniAbstract:How does a Quasicrystal grow? Despite the decades of research that have been dedicated to this area of study, it remains one of the fundamental puzzles in the field of crystal growth. Although there has been no lack of theoretical studies on Quasicrystal growth, there have been very few experimental investigations with which to test their various hypotheses. In particular, evidence of the in situ and three-dimensional (3D) growth of a Quasicrystal from a parent liquid phase is lacking. To fill-in-the-gaps in our understanding of the solidification and melting pathways of Quasicrystals, we performed synchrotron-based X-ray imaging experiments on a decagonal phase with composition of Al-15at%Ni-15at%Co. High-flux X-ray tomography enabled us to observe both growth and melting morphologies of the 3D Quasicrystal at temperature. We determined that there is no time-reversal symmetry upon growth and melting of the decagonal Quasicrystal. While Quasicrystal growth is predominantly dominated by the attachment kinetics of atomic clusters in the liquid phase, melting is instead barrier-less and limited by buoyancy-driven convection. These experimental results provide the much-needed benchmark data that can be used to validate simulations of phase transformations involving this unique phase of matter.
