Chemical Bonding and Physical Properties in Quasicrystals and Their Related Approximant Phases: Known Facts and Current Perspectives

Barber, Enrique Alfonso Maciá

doi:10.3390/app9102132

Cited by 12 publications

(5 citation statements)

References 116 publications

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“…These materials contain structurally complex phases including quasicrystals. The structurally complex phases have non-periodically ordered atomic arrangements [45,46]. Consequently, the properties of CMA are different from those observed in traditional materials [43].…”

Section: Introductionmentioning

confidence: 98%

Oxidation of Al-Co Alloys at High Temperatures

et al. 2020

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In this work, the high temperature oxidation behavior of Al71Co29 and Al76Co24 alloys (concentration in at.%) is presented. The alloys were prepared by controlled arc-melting of Co and Al granules in high purity argon. The as-solidified alloys were found to consist of several different phases, including structurally complex m-Al13Co4 and Z-Al3Co phases. The high temperature oxidation behavior of the alloys was studied by simultaneous thermal analysis in flowing synthetic air at 773–1173 K. A protective Al2O3 scale was formed on the sample surface. A parabolic rate law was observed. The rate constants of the alloys have been found between 1.63 × 10−14 and 8.83 × 10−12 g cm−4 s−1. The experimental activation energies of oxidation are 90 and 123 kJ mol−1 for the Al71Co29 and Al76Co24 alloys, respectively. The oxidation mechanism of the Al-Co alloys is discussed and implications towards practical applications of these alloys at high temperatures are provided.

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Section: Introductionmentioning

confidence: 98%

Oxidation of Al-Co Alloys at High Temperatures

et al. 2020

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“…28−30 Similarly, quasicrystal approximants (ACs) are conventional crystalline polar intermetallic phases that exhibit local structural motifs with similar forbidden rotational symmetries, analogous chemical compositions, and comparable e/a values. 31,32 The challenge with using e/a to understand polar intermetallics is that calculating the e/a ratio is not often straightforward for metallic systems. 33,34 A perfect example of this breakdown stems from several studies of gold intermetallic phases.…”

Section: Introductionmentioning

confidence: 99%

“…For instance, polar intermetallics are known to form quasicrystalline phases that display forbidden rotational symmetries (5-, 8-, 12-fold, etc. ). − Similarly, quasicrystal approximants (ACs) are conventional crystalline polar intermetallic phases that exhibit local structural motifs with similar forbidden rotational symmetries, analogous chemical compositions, and comparable e/a values. , The challenge with using e/a to understand polar intermetallics is that calculating the e/a ratio is not often straightforward for metallic systems. , …”

Section: Introductionmentioning

confidence: 99%

From Laves Phases to Quasicrystal Approximants in the Na–Au–Cd System

2023

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The exploratory synthesis of gold-based polar intermetallic phases has revealed many new compounds with unprecedented crystal structures, unique bonding arrangements, and interesting electronic features. Here, we further understand the complexity of gold’s crystal chemistry by studying the Na–Au–Cd ternary composition space. A nearly continuous structure transformation is observed between the seemingly simple binary NaAu2–NaCd2 phases, yielding three new intermetallic compounds with the compositions Na(Au0.89(5)Cd0.11(5))2, Na(Au0.51(4)Cd0.49(4))2, and Na8Au3.53(1)Cd13.47(1). Two compounds adopt different Laves phases, while the third crystallizes in a complex decagonal quasicrystal approximant. All three compounds are related through Friauf–Laves polyhedral building units with the gold/cadmium ratio found to control the transition among the unique crystal structures. Electronic structure calculations subsequently revealed the metallic nature of all three compounds with a combination of polar covalent Na–(Au/Cd) interactions and covalent (Au/Cd)–(Au/Cd) bonding interactions stabilizing each structure. These results highlight the crystal and electronic structure relationship among Laves phases and quasicrystal approximants enabled by the unique chemistry of gold.

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“…Since the discovery of quasicrystals in 1984, their unique crystal structure, and physical properties (including electronic, − thermal, , magnetic, , and thermoelectric , properties) have been widely investigated. However, the relationship between the valence states and the structure of quasicrystals and their approximants has not yet been clarified.…”

Section: Introductionmentioning

confidence: 99%

Three-Center Bonds in an Al–Pd–Co Quasicrystalline Approximant: Wannier Function-Based Chemical Bonding Analysis

Iwasaki,

Kimura,

Kitahara

2023

J. Phys. Chem. C

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The relationship between the valence electronic state and crystal structure of aluminum−transition-metal quasicrystals and their approximants remains to be elucidated. The origin of the semiconducting band structure on the Katz−Gratias− Boudard-type 1/1 approximants has yet to be clarified. We calculated the electronic structure of an Al−Pd−Co 1/1 quasicrystalline approximant (Al 92 Pd 8 Co 28 per unit cell) using density functional theory and analyzed the approximant's valence orbital character by constructing maximally localized Wannier functions. Among the 304 Wannier functions constructed from the valence bands, 288 were localized around transition metal atoms and 12 were localized between two Co atoms. The other four functions were localized around the center of three-membered rings of Co atoms, which indicates the presence of three-center bonds in this approximant. This situation is an exception to the Yannello− Fredrickson and Kitahara's electron rules, which explain the valence electronic states of aluminum−transition metal approximants and their related intermetallic compound semiconductors considering only two-center bonds. In this study, these rules are expanded to consider three-center bonds, making it possible to explain the semiconducting origin. This work indicates that the electron rule considering three-center bonds can be applied to quasicrystals and other approximants that have triangle networks.

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Chemical Bonding and Physical Properties in Quasicrystals and Their Related Approximant Phases: Known Facts and Current Perspectives

Cited by 12 publications

References 116 publications

Oxidation of Al-Co Alloys at High Temperatures

Oxidation of Al-Co Alloys at High Temperatures

From Laves Phases to Quasicrystal Approximants in the Na–Au–Cd System

Three-Center Bonds in an Al–Pd–Co Quasicrystalline Approximant: Wannier Function-Based Chemical Bonding Analysis

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