Experimental Demonstration of an Electride as a 2D Material

Druffel, Daniel L.; Kuntz, Kaci L.; Woomer, Adam H.; Alcorn, Francis M.; Hu, Jun; Donley, Carrie L.; Warren, Scott C.

doi:10.1021/jacs.6b10114

Cited by 160 publications

(153 citation statements)

References 40 publications

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“…Still, the binding energy of Y 2 CF 2 is less than that of other layered crystals, for example Ca 2 N (1.11 J/m 2 ), that have been exfoliated successfully into 2D flakes. 53 These calculations suggest that it may be possible to exfoliate Y 2 CF 2 into 2D flakes, although with somewhat greater difficulty than van der Waals crystals like Y 2 CCl 2 or graphite.…”

Section: Synthesis and Crystal Structurementioning

confidence: 93%

Synthesis and Electronic Structure of a 3D Crystalline Stack of MXene-Like Sheets

et al. 2019

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Despite the interest in MXenes in the last decade, all of the MXenes reported have a random mixture of surface terminations (-O, -OH, -F). In addition, restacked 3D films have turbostratic disorder and often contain ions, solvent, and other species in between their layers. Here we report Y 2 CF 2 , a layered crystal with a unit cell isostructural to a MXene, in which layers are capped only by fluoride anions. We directly synthesize the 3D crystal through a high-temperature solid-state reaction, which affords the 3D crystal in high yield and purity and ensures that only fluoride ions terminate the layers.We characterize the crystal structure and electronic properties using a combination of experimental and computational techniques. We find that relatively strong electrostatic 1 arXiv:1909.01490v1 [cond-mat.mtrl-sci] 3 Sep 2019 interactions bind the layers together into a 3D crystal and that the lack of orbital overlap between layers gives rise to a description of Y 2 CF 2 as slabs of MXene-like sheets electrically insulated from one another. Therefore, we consider Y 2 CF 2 as a pure 3D crystalline stack of MXene-like sheets. In addition, Y 2 CF 2 is the first transition metal carbide fluoride experimentally synthesized. We hope this work inspires further exploration of transition metal carbide fluorides, which are potentially a large and useful class of compositions.

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Section: Synthesis and Crystal Structurementioning

confidence: 93%

Synthesis and Electronic Structure of a 3D Crystalline Stack of MXene-Like Sheets

et al. 2019

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“…15,16 In recent years, Ca 2 N has been demonstrated to be an electride by electron transport measurement and since then inorganic electrides have sprung up quickly. [17][18][19][20][21] According to the dimensionality of the anionic electrons confinement, e.g., zero-dimensional (0D) cavities, one-dimensional (1D) channels and twodimensional (2D) interlayers, the electrides can be conveniently classified. A large amount of electrides with different confinement dimensionalities have been identified recently by high-throughput calculations from all known inorganic materials.…”

Section: Introductionmentioning

confidence: 99%

Prediction of Stoner-Type Magnetism in Low-Dimensional Electrides

Sui¹,

Wang

Duan³

2019

J. Phys. Chem. C

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Electrides are special ionic solids with excess cavity-trapped electrons serving as anions. Despite the extensive studies on electrides, the interplay between electrides and magnetism is not well understood due to the lack of stable magnetic electrides, particularly the lack of inorganic magnetic electrides. Here, based on the mechanism of Stonertype magnetic instability, we propose that in certain electrides the low-dimensionality can facilitate the formation of magnetic ground state because of the enhanced density of states near the Fermi level. To be specific, A 5 B 3 (A = Ca, Sr, Ba; B = As, Sb, Bi) (1D), Sr 11 Mg 2 Si 10 (0D), Ba 7 Al 10 (0D) and Ba 4 Al 5 (0D) have been identified as stable magnetic electrides with spin-polarization energies of tens to hundreds of meV per formula unit. Especially for Ba 5 As 3 , the spin-polarization energy can reach up to 220 meV. Furthermore, we demonstrate that the magnetic moment and spin density mainly derive from the interstitial anionic electrons near the Fermi level. Our work paves a way to the searching of stable magnetic electrides and further exploration of the magnetic properties and related applications in electrides.

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“…Since first crystalline organic electride of Cs + (18‐crown‐6) 2 e − was synthesized by Ahmed et al in 1983,1 many attempts have been made to obtain the stable organic electrides to further understand the nearly‐free electron behaviors and their geometrical topologies. The discovery of room‐temperature stable inorganic electride [Ca 24 Al 28 O 64 ] 4+ ·4e − (C12A7)2 has drawn much attention to electride materials due to the promising practical applications and the substantial amounts of studies have been carried out to find new electrides 3. Dicalcium nitride (Ca 2 N) and yttrium hypocarbide (Y 2 C) were demonstrated subsequently as a new class of two‐dimensional (2D) electrides in experiments.…”

Section: Introductionmentioning

confidence: 99%

Metal‐to‐Semiconductor Transition and Electronic Dimensionality Reduction of Ca₂N Electride under Pressure

et al. 2018

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The discovery of electrides, in particular, inorganic electrides where electrons substitute anions, has inspired striking interests in the systems that exhibit unusual electronic and catalytic properties. So far, however, the experimental studies of such systems are largely restricted to ambient conditions, unable to understand their interactions between electron localizations and geometrical modifications under external stimuli, e.g., pressure. Here, pressure‐induced structural and electronic evolutions of Ca2N by in situ synchrotron X‐ray diffraction and electrical resistance measurements, and density functional theory calculations with particle swarm optimization algorithms are reported. Experiments and computation are combined to reveal that under compression, Ca2N undergoes structural transforms from R 3true¯ m symmetry to I 4true¯2d phase via an intermediate Fd 3true¯ m phase, and then to Cc phase, accompanied by the reductions of electronic dimensionality from 2D, 1D to 0D. Electrical resistance measurements support a metal‐to‐semiconductor transition in Ca2N because of the reorganizations of confined electrons under pressure, also validated by the calculation. The results demonstrate unexplored experimental evidence for a pressure‐induced metal‐to‐semiconductor switching in Ca2N and offer a possible strategy for producing new electrides under moderate pressure.

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Experimental Demonstration of an Electride as a 2D Material

Cited by 160 publications

References 40 publications

Synthesis and Electronic Structure of a 3D Crystalline Stack of MXene-Like Sheets

Synthesis and Electronic Structure of a 3D Crystalline Stack of MXene-Like Sheets

Prediction of Stoner-Type Magnetism in Low-Dimensional Electrides

Metal‐to‐Semiconductor Transition and Electronic Dimensionality Reduction of Ca₂N Electride under Pressure

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Experimental Demonstration of an Electride as a 2D Material

Cited by 160 publications

References 40 publications

Synthesis and Electronic Structure of a 3D Crystalline Stack of MXene-Like Sheets

Synthesis and Electronic Structure of a 3D Crystalline Stack of MXene-Like Sheets

Prediction of Stoner-Type Magnetism in Low-Dimensional Electrides

Metal‐to‐Semiconductor Transition and Electronic Dimensionality Reduction of Ca2N Electride under Pressure

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Product

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Metal‐to‐Semiconductor Transition and Electronic Dimensionality Reduction of Ca₂N Electride under Pressure