Raman investigations and ab initio calculations of natural diamond-lonsdaleite originating from New Caledonia

Mendili, Yassine El; Orberger, B.; Chateigner, Daniel; Bardeau, Jean‐François; Gascoin, Stéphanie; Petit, Sébastien

doi:10.1016/j.chemphys.2022.111541

Cited by 9 publications

(1 citation statement)

References 52 publications

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“…However, despite the conditions of its appearance and its structural peculiarities, it remains a bit controversial and questioned, as it is considered as cubic diamond dominated by extensive stacking faults and twins [ 20 ]. Indeed, at the present time, pure lonsdaleite has never been found or synthesized as single crystal or in bulk form; and its presence, either from natural origin or produced artificially, namely synthesized in a laboratory under thermobaric (high dynamic/static pressure—high temperature, HP-HT) conditions [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ], has been usually observed only in small amounts and as nanoparticles inside diamond crystals. Similarly to the structure of both cubic diamond and hexagonal lonsdaleite, in which each sp 3-hybridized carbon atom is bonded to four other carbon atoms, Cu2 and Cu3 atoms form a tetrahedral structure resulting in a 3D rigid network with strong chemical bonds.…”

Section: Resultsmentioning

confidence: 99%

Cu3As: Uncommon Crystallographic Features, Low-Temperature Phase Transitions, Thermodynamic and Physical Properties

et al. 2023

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The formation and crystal structure of the binary Cu3As phase have been re-investigated. Some physical properties were then measured on both single crystal and polycrystalline bulk. Cu3As melts congruently at 835 °C. At room temperature (RT), this compound has been found to crystallize in the hexagonal Cu3P prototype (hP24, P63cm) with lattice parameters: a = 7.1393(1) Å and c = 7.3113(1) Å, rather than in the anti HoH3-type (hP24, P–3c1) as indicated in literature. A small compositional range of 74.0–75.5 at.% Cu (26.0–24.5 at.% As) was found for samples synthesized at 300 and 400 °C; a corresponding slight understoichiometry is found in one out of the four Cu atomic sites, leading to the final refined composition Cu2.882(1)As. The present results disprove a change in the crystal structure above RT actually reported in the phase diagram (from γ’ to γ on heating). Instead, below RT, at T = 243 K (−30 °C), a first-order structural transition to a trigonal low-temperature superstructure, LT-Cu3−xAs (hP72, P–3c1) has been found. The LT polymorph is metrically related to the RT one, having the c lattice parameter three times larger: a = 7.110(2) Å and c = 21.879(4) Å. Both the high- and low-temperature polymorphs are characterized by the presence of a tridimensional (3D) uncommon and rigid Cu sublattice of the lonsdaleite type (Cu atoms tetrahedrally bonded), which remains almost unaffected by the structural change(s), and characteristic layers of triangular ‘Cu3As’-units (each hosting one As atom at the center, interconnected each other by sharing the three vertices). The first-order transition is then followed by an additional structural change when lowering the temperature, which induces doubling of also the lattice parameter a. Differential scanning calorimetry nicely detects the first low-temperature structural change occurring at T = 243 K, with an associated enthalpy difference, ΔH(TR), of approximately 2 J/g (0.53 kJ/mol). Low-temperature electrical resistivity shows a typical metallic behavior; clear anomalies are detected in correspondence to the solid-state transformations. The Seebeck coefficient, measured as a function of temperature, highlights a conduction of n-type. The temperature dependence of the magnetic susceptibility displays an overall constant diamagnetic response.

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Section: Resultsmentioning

confidence: 99%

Cu3As: Uncommon Crystallographic Features, Low-Temperature Phase Transitions, Thermodynamic and Physical Properties

et al. 2023

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Research on the chemical barrier and failure behavior of WS2 and WS2/Ti coatings under high-temperature conditions and the effects on the lifespan of diamond-coated cutting tools

Zhang

Tan

et al. 2023

Surface and Coatings Technology

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A density functional theory study of nitrogen vacancy center in lonsdaleite

Abdelghafar,

Choi,

Askar

2024

J. Phys. D: Appl. Phys.

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Lonsdaleite is a carbon allotrope and metastable form of diamond that demonstrates superior mechanical properties over cubic diamond. Here, we report the results of density functional theory (DFT) and molecular dynamics (MD) study of neutral and negative nitrogen vacancy center in lonsdaleite. Interestingly, neutral (NV0) and negative (NV-1) nitrogen-vacancy center in lonsdaleite display a remarkable splitting in the two degenerate ex and ey excited states nearly around ~ 0.5 eV for NV0 and 0.2 eV for NV-1. The thermal stability, dynamic stability, band structure, density of states, and optical properties are computed. The DFT and MD calculations reveal that geometrical structure of NV center in lonsdaleite is both thermally and dynamically stable. In addition, the findings show that NV0 and NV-1centers in lonsdaleite demonstrate splitting in the zero-phonon line (ZPL) due to symmetry reduction from C3v to C1h with respect to NV center in cubic diamond. Furthermore, the results indicate that ZPL falls around ~ 1.76 and 2.25 eV for NV0, while it lies around 1.91 and 2.19 eV for NV-1.

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Raman investigations and ab initio calculations of natural diamond-lonsdaleite originating from New Caledonia

Cited by 9 publications

References 52 publications

Cu3As: Uncommon Crystallographic Features, Low-Temperature Phase Transitions, Thermodynamic and Physical Properties

Cu3As: Uncommon Crystallographic Features, Low-Temperature Phase Transitions, Thermodynamic and Physical Properties

Research on the chemical barrier and failure behavior of WS2 and WS2/Ti coatings under high-temperature conditions and the effects on the lifespan of diamond-coated cutting tools

A density functional theory study of nitrogen vacancy center in lonsdaleite

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