Low temperature study of the structural stability, electronic and optical properties of the acanthite α-Ag2S: Spin-orbit coupling effects and new important ultra-refraction property

Fouddad, Fatma Zohra; Hiadsi, S.; Latifa, Bouzid; Ghrici, Yacine Foad; Bekhadda, Kheira

doi:10.1016/j.mssp.2019.104801

Cited by 13 publications

(6 citation statements)

References 48 publications

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“…Crystallographic parameters are fundamental parameters that describe the crystal structure and the internal atomic arrangement, which are crucial for determining the structural, physicochemical properties of materials and are typically relatively fixed. However, due to the special occupancy of Ag in α-Ag2S, the crystallographic parameter data from five sets of experiments [20][21][22] and theoretical calculations 3,23 listed in Table 1 show strong dispersion (especially for c and β), among which the experimental values from Blanton et al 22 are close to our calculations.…”

Section: Results Potential Validationsupporting

confidence: 78%

“…As the first reported room-temperature ductile semiconductor, polycrystalline α-Ag2S has been shown to withstand enormous plastic deformation, particularly without fracture under 50% compressive strain. The excellent optical properties 3 , outstanding environmental compatibility 4 , improvable thermoelectric figure of merit 5 , and ultra-strong deformation capacity of α-Ag2S make it highly promising for thermoelectric materials and flexible electronic devices. In recent years, based on α-Ag2S, Shi et al [6][7][8][9][10][11][12] have achieved the tuning of ionic/covalent bond characteristics through elemental substitution (doping with Cu, Se, Te, etc.…”

Section: Introductionmentioning

confidence: 99%

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Atomic perspective on plasticity mechanism of ionic-covalent systems from machine learning molecular dynamics simulations

Hu,

Yang,

Peng

et al. 2024

Preprint

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Due to the diversity of atomic bonding, good plasticity is often considered a hallmark characteristic of metals. Novel plastic inorganic semiconductors like α-Ag2S have challenged this conventional thinking, but relevant first-principles calculations still lack an intuitive and comprehensive understanding of the underlying plasticity mechanisms. From the perspective of machine learning molecular dynamics that can describe the microstructure evolution aptly, this work reveals the plasticity mechanism of the ionic-covalent system α-Ag2S. Shear bands or kink bands originating from random and local micro-kinks signify the plastic features, and the subsequent amorphization enables sustained deformation under high strains. Different from features in metals, the oppositely signed dislocation pairs in α-Ag2S can achieve nucleation and motion through coordinated lattice expansion and contraction, while the twining-like kink triggered in a staggered manner allows the material to accommodate large shear strains. The established idealized models capture the unconventional dislocation pair and pseudo-twinning kink, narrowing the blind area in our understanding of plasticity mechanisms within similar systems. The summarized structural and deformation features provide clear clues for identifying other plastic ionic-covalent crystals in superionic conductors.

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Section: Results Potential Validationsupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Atomic perspective on plasticity mechanism of ionic-covalent systems from machine learning molecular dynamics simulations

Hu,

Yang,

Peng

et al. 2024

Preprint

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“…It can be seen that no other diffraction peaks exist, which means that no other phases or other impurities are mixing in the sample. The Rietveld refinement of the XRD pattern at ambient pressure yields a = 4.214 ± 0.001 Å, b = 6.912 ± 0.001 Å, c = 7.853 ± 0.001 Å, β = 99.580° ± 0.010°, V 0 = 225.55 ± 0.034 Å 3 for Ag 2 S nanosheets, slightly smaller than 30 nm Ag 2 S nanoparticles and bulk materials [ 27 , 28 ]. The existence of a lattice shrinking phenomenon of Ag 2 S nanosheets could be attributed to the stronger nanosize effect as a result of their smaller thickness.…”

Section: Resultsmentioning

confidence: 99%

High-Pressure Behaviors of Ag2S Nanosheets: An in Situ High-Pressure X-Ray Diffraction Research

Liu

et al. 2020

Nanomaterials

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An in situ high-pressure X-ray diffraction study was performed on Ag2S nanosheets, with an average lateral size of 29 nm and a relatively thin thickness. Based on the experimental data, we demonstrated that under high pressure, the samples experienced two different high-pressure structural phase transitions up to 29.4 GPa: from monoclinic P21/n structure (phase I, α-Ag2S) to orthorhombic P212121 structure (phase II) at 8.9 GPa and then to monoclinic P21/n structure (phase III) at 12.4 GPa. The critical phase transition pressures for phase II and phase III are approximately 2–3 GPa higher than that of 30 nm Ag2S nanoparticles and bulk materials. Additionally, phase III was stable up to the highest pressure of 29.4 GPa. Bulk moduli of Ag2S nanosheets were obtained as 73(6) GPa for phase I and 141(4) GPa for phase III, which indicate that the samples are more difficult to compress than their bulk counterparts and some other reported Ag2S nanoparticles. Further analysis suggested that the nanosize effect arising from the smaller thickness of Ag2S nanosheets restricts the relative position slip of the interlayer atoms during the compression, which leads to the enhancing of phase stabilities and the elevating of bulk moduli.

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“…[84] Noticeably, the mobility can reach 10 2 -10 3 cm 2 V −1 s −1 for these materials. [85][86][87][88][89] The reduced ionicity of AgQ bonds may also promote the formation of crystal defects (Ag interstitials or Q vacancies), [90,91] which contributes to a large increase in electron density from the order of 10 14 cm −3 in Ag 2 S to 10 18 cm −3 in Ag 2 Se or Ag 2 Te. For the mechanical and thermodynamic properties, the melting point and the bulk modulus increase from Ag 2 S to Ag 2 Te, which reflects the increased bonding stiffness.…”

Section: Fundamental Physical Properties and Thermoelectric Performancementioning

confidence: 99%

Ag₂Q‐Based (Q = S, Se, Te) Silver Chalcogenide Thermoelectric Materials

et al. 2022

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should have a high electrical conductivity (σ), a high Seebeck coefficient (S), and a low thermal conductivity (κ). [6][7][8][9] Cu 2 Q-and Ag 2 Q-based (Q = S, Se, Te) chalcogenides are exemplified with partially decoupled electrical and thermal transports. Over the past decade, Cu 2 Q materials have been widely investigated, showcasing remarkable zT values (around 2.0) at high temperatures. [10][11][12][13][14] As the homologous compounds sharing some common features, Ag 2 Q-based silver chalcogenides have arisen as a new spotlight in thermoelectrics (Figure 1) in recent years. Notably, the high zT values near unity of Ag 2 Se [15][16][17] make it a potential candidate for room-temperature thermoelectric application. In fact, Ag 2 Q compounds are "old" materials whose discovery can be traced back to the 19th century. [18][19][20] Their thermoelectric properties were first reported in the 1940s-1960s during which decent performance of Ag 2 Se and Ag 2 Te was unveiled. [21][22][23][24][25][26] After that, the study on Ag 2 Q had faded out over decades accompanying the low ebb of thermoelectric research. [27,28] Upon the turn of the century, especially over the last 10 years, the revival has come for thermoelectrics, bringing about great progress in transport theories, [29][30][31][32][33] advanced synthesis, [34][35][36][37] and characterization techniques, [38][39][40] and even the research paradigm. [41][42][43] All these progresses have boosted zT from 1 to 2 in not a few new or old thermoelectric materials. [44][45][46][47][48] In the same period, the booming of flexible/wearable electronics necessitates thermoelectric materials having both high performance and deformability at room temperature. [49][50][51][52] All these factors inspire people to revisit Ag 2 Q-based materials.Ag 2 Q-based materials exhibit a low lattice thermal conductivity originating from the large disorder or even liquid-like behavior of Ag ions. [53][54][55][56] They tend to show n-type conduction with a high electron mobility. [15,57,58] Apart from the thermoelectric properties, an exceptional room-temperature plasticity has been found in Ag 2 S-based materials (Figure 1), [59] which is quite rare and valuable for inorganic semiconductors. [60] Beyond the binary compounds, several ternary and even quaternary Ag 2 (S, Se, Te) alloys have been developed, exhibiting both high zT values and excellent plastic deformability. [54,[61][62][63] In addition, CuAgQ materials, the intermediate compounds between Ag 2 Q and Cu 2 Q, have also received wide attention as promising thermoelectric materials. [64][65][66][67] Considering the new, intriguing scientific issues and great application prospects of Ag 2 Q-based silver chalcogenide thermoelectric materials, here in this review, we try to provide the Thermoelectric technology provides a promising solution to sustainable energy utilization and scalable power supply. Recently, Ag 2 Q-based (Q = S, Se, Te) silver chalcogenides have come forth as potential thermoelectric materials that are endowed wi...

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Low temperature study of the structural stability, electronic and optical properties of the acanthite α-Ag2S: Spin-orbit coupling effects and new important ultra-refraction property

Cited by 13 publications

References 48 publications

Atomic perspective on plasticity mechanism of ionic-covalent systems from machine learning molecular dynamics simulations

Atomic perspective on plasticity mechanism of ionic-covalent systems from machine learning molecular dynamics simulations

High-Pressure Behaviors of Ag2S Nanosheets: An in Situ High-Pressure X-Ray Diffraction Research

Ag₂Q‐Based (Q = S, Se, Te) Silver Chalcogenide Thermoelectric Materials

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Low temperature study of the structural stability, electronic and optical properties of the acanthite α-Ag2S: Spin-orbit coupling effects and new important ultra-refraction property

Cited by 13 publications

References 48 publications

Atomic perspective on plasticity mechanism of ionic-covalent systems from machine learning molecular dynamics simulations

Atomic perspective on plasticity mechanism of ionic-covalent systems from machine learning molecular dynamics simulations

High-Pressure Behaviors of Ag2S Nanosheets: An in Situ High-Pressure X-Ray Diffraction Research

Ag2Q‐Based (Q = S, Se, Te) Silver Chalcogenide Thermoelectric Materials

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Product

Resources

About

Ag₂Q‐Based (Q = S, Se, Te) Silver Chalcogenide Thermoelectric Materials