Precise in situ study of the kinetics of pressure-induced phase transition in CaF2 including initial transformation stages

El’kin, F. S.; Tsiok, O. B.; Khvostantsev, L. G.; Бражкин, В. В.

doi:10.1134/1.1947320

Cited by 15 publications

(17 citation statements)

References 12 publications

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“…The transition is accompanied by a collapse of the unit cell volumes by 13.6%, 8.16%, 5.7% and 8.81% for LDA, PBE, CENT and BMH, respectively, comparable to the experimental value of 8.3% given in Ref. [64].…”

Section: A Bulk Propertiessupporting

confidence: 86%

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High accuracy and transferability of a neural network potential through charge equilibration for calcium fluoride

et al. 2017

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We investigate the accuracy and transferability of a recently developed high dimensional neural network (NN) method for calcium fluoride, fitted to a database of ab initio density functional theory (DFT) calculations based on the Perdew-Burke-Ernzerhof (PBE) exchange correlation functional. We call the method charge equilibration via neural network technique (CENT). Although the fitting database contains only clusters (i.e. non-periodic structures), the NN scheme accurately describes a variety of bulk properties. In contrast to other available empirical methods the CENT potential has a much simpler functional form, nevertheless it correctly reproduces the PBE energetics of various crystalline phases both at ambient and high pressure. Surface energies and structures as well as dynamical properties derived from phonon calculations are also in good agreement with PBE results. Overall, the difference between the values obtained by the CENT potential and the PBE reference values is less than or equal to the difference between the values of local density approximation (LDA) and Born-Mayer-Huggins (BMH) with those calculated by the PBE exchange correlation functional.

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Section: A Bulk Propertiessupporting

confidence: 86%

“…[49,51,52,55,57,[61][62][63][64]). Cubic F m3m is known to transform into the orthorhombic P nma phase at a pressure between 8 and 10 GPa, accompanied by an increase of the coordination number of Ca from 8 to 9.…”

Section: A Bulk Propertiesmentioning

confidence: 99%

High accuracy and transferability of a neural network potential through charge equilibration for calcium fluoride

et al. 2017

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“…The reduced exponent value below 3 can be attributed to the anisotropic growth and blocking effects, or it could be an outcome of a mixture of 3D and 2D growth with site saturation [48][49][50][51] . In theory, polymorphic phase transformations are categorized as either displacive (rapid and diffusionless) or reconstructive (slow and diffusion limited) [52][53][54] . In practice, assumptions regarding diffusion, preferred nucleation sites such as defects, grain boundaries, or dislocations, and experimentally determined crystal growth habit (i.e., spherical, disc, or rod growth) are required to make reliable inferences from the JMAK exponent.…”

Section: Discussionmentioning

confidence: 99%

Mechanochemical conversion kinetics of red to black phosphorus and scaling parameters for high volume synthesis

et al. 2020

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Adopting black phosphorus (BP) as a material in electronic and optoelectronic device manufacturing requires the development and understanding of a large-scale synthesis technique. To that end, high-energy planetary ball milling is demonstrated as a scalable synthesis route, and the mechanisms and conversion kinetics of the BP phase transformation are investigated. During the milling process, media collisions rapidly compress amorphous red phosphorus (RP) into crystalline, orthorhombic BP flakes, resulting in a conversion yield of ≈90% for ≈5 g of bulk BP powder. Milling conversion kinetics, monitored via ex situ x-ray diffraction, manifest a sigmoidal behavior best described by the Avrami rate model with each impact of sufficient energy (>25 mJ) producing BP nuclei; the process appears to be limited by grain growth. Using a kinematic model for ball trajectories and impact energies, the optimum milling condition is determined to be an impact energy near ≈25 mJ and a milling dose near ≈100 kJ/gram. Photoexcitation of exfoliated BP flakes reveals emission in the near-infrared, indicating the formation of few-layer BP, a promising advance for optoelectronic device applications.

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“…The Fm3m to Pnma structural phase transition has already been observed experimentally, 14,19 for example, but the transition to P6 3 / mmc has not yet been detected for CaF 2 . Although CaF 2 is ionic at ambient condi-tions, it is important to look for the Ni 2 In phase in the context of understanding its possible metallization at high pressures; AuIn 2 thus serves as a relevant analog compound for experimental study.…”

mentioning

confidence: 82%

“…[13][14][15][16][17][18][19][20][21][22][23] These studies show that CaF 2 transforms from the face-centered cubic fluorite structure ͑Fm3m͒ to an orthorhombic PbCl 2 -type ͑Pnma͒ structure at pressures between 8 and 10 GPa. Some electronic-structure calculations indicate that the band gap of CaF 2 increases with pressure, [20][21][22] becoming a direct gap due to the Fm3m to Pnma transition and then showing signatures of band-overlap metallization near 210 GPa.…”

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confidence: 99%

Postcotunnite phase of the intermetallic compoundAuIn2at high pressure

et al. 2010

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We report a structural phase transition in AuIn 2 above 25 GPa. The inferred structure of this phase is post cotunnite ͑P112 1 / a͒. Combining the new results with previously observed behavior of AuIn 2 , we propose a sequence of structural transitions from CaF 2 ͑Fm3m͒ to amorphous phase at 24 GPa to monoclinic ͑P112 1 / a͒ structure at 25.6 GPa. During decompression the high-pressure phase is preserved to the pressure of 9.4 GPa and it finally transforms back to the Fm3m phase. Analysis of volume reduction and bulk modulus increase reveals close similarity with the postcotunnite phase observed in PbCl 2 . This study is important in understanding the behavior of metallic phases of various oxides of geophysical interest which exist in CaF 2 fluorite-type structure.

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Precise in situ study of the kinetics of pressure-induced phase transition in CaF2 including initial transformation stages

Cited by 15 publications

References 12 publications

High accuracy and transferability of a neural network potential through charge equilibration for calcium fluoride

High accuracy and transferability of a neural network potential through charge equilibration for calcium fluoride

Mechanochemical conversion kinetics of red to black phosphorus and scaling parameters for high volume synthesis

Postcotunnite phase of the intermetallic compoundAuIn2at high pressure

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