Lattice vibrations of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>γ</mml:mi></mml:math>- and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>β</mml:mi></mml:math>-coronene from Raman microscopy and theory

Bannister, Nicola; Skelton, Jonathan M.; Kociok‐Köhn, Gabriele; Batten, Tim; Como, Enrico Da; Crampin, S.

doi:10.1103/physrevmaterials.3.125601

Cited by 4 publications

(7 citation statements)

References 48 publications

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“…Moreover, ab initio modeling techniques have recently been employed in predicting phonon-related spectra, − including Raman, and infrared, facilitating the usage of theory to interpret experiments. A large and growing body of the literature covers the prediction of vibrational modes and Raman spectra from first-principle techniques, ,− providing a valuable aid to experimental characterization. For example, a recent theoretical work reported Raman spectra of six Bi-O-X materials with similar layer crystal structures: Bi 2 O 2 X and Bi 2 OX 2 (X = S, Se, and Te), which could help to identify the crystal structures experimentally.…”

Section: Introductionmentioning

confidence: 99%

Raman Spectroscopy Signatures of Boron-Rich Superhard Materials from Density Functional Theory

Shen

Tang

et al. 2023

J. Phys. Chem. C

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Boron-rich superhard materials have complex structural and chemical variations, making it challenging to determine their atomic structures precisely from experiments. Here, we employ first-principles calculation to examine Raman spectra of four boron-rich icosahedral crystals: boron carbide (B 4 C), boron-rich boron carbide (B 13 C 2 ), boron suboxide (B 6 O), and boron subphosphide (B 12 P 2 ). We find qualitative agreements in Raman peak locations between the calculated Raman spectra and the experimental measurements. Furthermore, vibrations of the icosahedra or chains, occurring in all the spectra, are interpreted by performing vibration mode analyses. Our results indicate that the vibrations of the two-atom chain are responsible for the low-frequency region of B 6 O and B 12 P 2 . In contrast, both low-frequency and high-frequency regions are partially related to the vibration of chain atoms for B 4 C and B 13 C 2 . Besides, the icosahedral vibration modes are attributed to the high-frequency region of all these four crystals. More importantly, the peak positions of Raman spectra can be used to identify the various icosahedral structure with different B/C ratios and various chain structures, making Raman spectroscopy an important tool to monitor the processing of newly developed icosahedral materials with enhanced physical properties. This study not only provides a deeper understanding of the atomic structures of boron-rich superhard materials from the perspective of Raman spectroscopy but also helps to interpret the experimental Raman spectra.

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Section: Introductionmentioning

confidence: 99%

Raman Spectroscopy Signatures of Boron-Rich Superhard Materials from Density Functional Theory

Shen

Tang

et al. 2023

J. Phys. Chem. C

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“…At 0.2 GPa, two lattice modes (L 1 and L 2 ), which were particularly sensitive to phase transitions, split into doublets producing a spectrum that was a fingerprint of the β ‐polymorph. [ 19,27 ] The polymorph change at 0.2 GPa, coincided with a sharp increase in the PL intensity observed at the same pressure. At 0.8 GPa, the L 2a peak split and formed another doublet, indicating a structural change.…”

Section: Resultsmentioning

confidence: 55%

Full‐Color Luminescence from Single‐Component Hydrocarbon Crystal: RGB Emission by Altering Molecular Packing Under Pressure

Nakagawa,

Guo,

Vrankić

et al. 2023

Advanced Optical Materials

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Full‐color emission from solid single‐component organic materials is highly desired to realize inexpensive and non‐toxic organic electronics. However, as the three primary colors, red, green, and blue (RGB), have significantly different energies, observation of RGB luminescence from a single‐component molecule is extremely challenging. In this study, a coronene nanorod single‐component single‐crystal is prepared, which exhibits blue fluorescence at ambient conditions and realizes full‐color emission, for the first time, by altering the molecular packing through high‐pressure compression. A valuable insight into the relationships between structure and optical properties of coronene at high pressures is obtained by combining various spectroscopic studies. During compression, it is found that the tuneable piezochromic luminescence of coronene is strictly related to the molecular packing and crystallographic symmetry. This study not only provides insight into the structure‐optical property relationships of hydrocarbon but also promotes the development of single molecular systems with different molecular packing that exhibit RGB emissions even at ambient conditions even with a single excitation wavelength.

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“…The properties are calculated with the PBE functional, with relative lattice energies including the three specified dispersion corrections. The experimental temperature range of stability is from ref .…”

Section: Resultsmentioning

confidence: 99%

“…The size of a β coronene a crystal grown under a magnetic field 35 was sufficient to establish its structure by single-crystal X-ray diffraction. Calculation of the Raman spectra of the two forms has shown that the β form is the more stable phase of coronene at low temperatures, 37,38 which had not previously been characterized because the γ crystals shatter on cooling. Examination of the phase transition in different samples (SI, Section I.D) shows that the polymorphic transformation is dependent on crystal size.…”

Section: Crystal Growth and Designmentioning

confidence: 99%

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On the Application of Strong Magnetic Fields during Organic Crystal Growth

Potticary

Hall

Guo

et al. 2021

Crystal Growth & Design

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We investigate the effect of crystal growth within a magnetic field for three polymorphic pharmaceuticals, using an experiment where the magnetic field can be varied in strength without altering other crystallization conditions. In the case of carbamazepine, fields above 0.6 T produce metastable form I, and for flufenamic acid, there is an increased propensity to crystallize metastable form I around 1 T. In contrast, the magnetic field has no effect on the crystallization of mefenamic acid, a closely related molecule. The growth of the metastable β polymorph of coronene within a magnetic field at ambient temperature is difficult to reproduce but has been seen as a minor component, consistent with this transformation to the more stable form being facile, depending on the particle size. Calculations of the diamagnetic susceptibility tensors of the polymorphs and their morphologies provide semiquantitative estimates of how the diamagnetic susceptibilities of crystallites differ between polymorphs and explain why mefenamic acid crystallization is unaffected. As the onset of crystallization of carbamazepine and coronene, as defined by changes in turbidity, occur at lower temperatures and hence greater supersaturations in certain ranges of magnetic field strength, this suggests that the field causes precipitation of the metastable form through Ostwald’s rule of stages.

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Lattice vibrations ofγ- andβ-coronene from Raman microscopy and theory

Cited by 4 publications

References 48 publications

Raman Spectroscopy Signatures of Boron-Rich Superhard Materials from Density Functional Theory

Raman Spectroscopy Signatures of Boron-Rich Superhard Materials from Density Functional Theory

Full‐Color Luminescence from Single‐Component Hydrocarbon Crystal: RGB Emission by Altering Molecular Packing Under Pressure

On the Application of Strong Magnetic Fields during Organic Crystal Growth

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