High-resolution FTIR study of the para-terphenyl phase transition at high pressure

Schatschneider, Christopher; Chronister, Eric L.

doi:10.1016/j.jlumin.2007.02.059

Cited by 8 publications

(5 citation statements)

References 32 publications

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“…According to theoretical calculations and previous reported experimental results, in the doped crystal a pentacene molecule substitutes a position in place of a single p -terphenyl, being built with the same orientation and center of mass as that of the replaced p -terphenyl molecule . Below 193 K, there are four inequivalent lattice sites that pentacene may replace in the p -terphenyl crystal structure, labeled as M 1 , M 2 , M 3 , and M 4 shown in Figure e. ,,, At 193 K, there is a disorder–order phase transition when the rocking of the central rings of p -terphenyl is stabilized in one minimum potential, resulting the triclinic phase to become a monoclinic form at room temperature. , Such a related orientation in ordered matrix makes the transition dipole moment of the dopant molecule coincide with the that of the matrix, enabling researchers to analyze and regulate the anisotropic molecular properties of the dopant by manipulation of the host crystal. , …”

Section: Resultsmentioning

confidence: 83%

“…11,13,14,35 At 193 K, there is a disorder− order phase transition when the rocking of the central rings of p-terphenyl is stabilized in one minimum potential, resulting the triclinic phase to become a monoclinic form at room temperature. 36,37 Such a related orientation in ordered matrix makes the transition dipole moment of the dopant molecule coincide with the that of the matrix, enabling researchers to analyze and regulate the anisotropic molecular properties of the dopant by manipulation of the host crystal. 13,38 One more characteristic of the host p-terphenyl crystal is its intrinsic laminar structure.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Growth Regulation of Pentacene-Doped p-Terphenyl Crystals on Their Physical Properties for Promising Maser Gain Medium

Cui

Liu

Li³

et al. 2020

Crystal Growth & Design

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Doped organic crystals possess wide application potential in the fields of scintillators and maser gain medium. However, the growth of doped organic single crystals with bulk size and high quality is still a big challenge due to the well-known poor crystallization capacity for organic materials. Here we report a thermal field-elevating technique to realize optimized growth conditions for organic crystals, where a pentacene-doped p-terphenyl single crystal with a size of Φ18 mm × 80 mm is obtained. Crystal quality and doping concentration effect on the optical properties of the crystalline wafers are investigated. The results show that p-terphenyl single crystal as an ordered matrix not only separates the guest molecules from one another to prevent quenching, but also constructs a Shpolskii-type host as an orienting medium to increase the interaction of pentacene with light. Moreover, a slightly reducing growth atmosphere is found to generate longer excitation lifetimes and a larger magnetic susceptibility of the grown doped crystal, which may be favorable for the spin-related physical process occurring in the excited state.

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Section: Resultsmentioning

confidence: 83%

Section: ■ Results and Discussionmentioning

confidence: 99%

Growth Regulation of Pentacene-Doped p-Terphenyl Crystals on Their Physical Properties for Promising Maser Gain Medium

Cui

Liu

Li³

et al. 2020

Crystal Growth & Design

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“…The polymorphic phase transitions of PTP under variable temperature and pressure conditions have been studied via X-ray, − IR, − Raman, ,− optical absorption, neutron scattering, − time-resolved THz and optical spectroscopy, ,, NMR, and calorimetry. , In addition, molecular dynamics (MD) simulations, − pressure-dependent lattice dynamics, and ab initio calculations have been performed under high pressure…”

Section: Introductionmentioning

confidence: 99%

Molecular Simulation of the Pressure-Induced Crystallographic Phase Transition of p-Terphenyl

Schatschneider

Chronister

2010

J. Phys. Chem. B

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The pressure- and temperature-induced polymorphic crystal phase transitions of p-terphenyl (PTP) have been modeled using a modified PCFF interaction force field. Modifications of the interaction potential were necessary to simultaneously model both the temperature-induced phase transition at ambient pressure and the pressure-induced phase transition at low temperature. Although the high-temperature and high-pressure phases are both characterized by flattening of the PTP molecule, the mechanisms of the temperature- and pressure-induced phase transitions are different. At high temperature thermal energy exceeds the torsional barrier, resulting in a bimodal phenyl ring twist angle distribution that averages to zero. In contrast, compression of PTP at high pressure results in a static planar structure. At high pressure the compression of the unit cell is also characterized by large compression of the a lattice parameter and weak compression of c, but some expansion of the b lattice parameter. The expansion of the b lattice parameter is likely associated with pressure-induced soft mode behavior of some lattice vibrations as well as soft mode behavior of pseudolocal phonons associated with impurities in PTP. The crystallographic angles α, β, and γ also indicate a triclinic crystal phase above the critical phase transition pressure of P(c) ~ 0.5 GPa at low temperature, suggesting a distinct phase separate from the monoclinic high-pressure phase at high temperature.

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“…When pressure is applied, the molecules become planar by ∼0.5 GPa, similar to para-terphenyl. 73,74 This results in rearrangement of the crystal matrix as demonstrated by the decrease in the C•••C contacts up to ∼2 GPa in Figure 23. The flattening of the molecules and decrease in C•••C contacts correlates with the decrease in the conduction band dispersion in Figure 22.…”

Section: Methodsmentioning

confidence: 96%

“…In contrast, in the triclinic phase, the molecules adopt a twisted conformation and the crystal structure has some C···C intermolecular contacts at 0 GPa. When pressure is applied, the molecules become planar by ∼0.5 GPa, similar to para -terphenyl. , This results in rearrangement of the crystal matrix as demonstrated by the decrease in the C···C contacts up to ∼2 GPa in Figure . The flattening of the molecules and decrease in C···C contacts correlates with the decrease in the conduction band dispersion in Figure .…”

Section: Computational Methodsmentioning

confidence: 96%

High-Throughput Pressure-Dependent Density Functional Theory Investigation of Herringbone Polycyclic Aromatic Hydrocarbons: Part 2. Pressure-Dependent Electronic Properties

et al. 2018

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Understanding the effect intermolecular interactions have on the electronic properties of highly conjugated/aromatic organic networks is important for optimizing these materials for optoelectronic device applications. Here, dispersion inclusive density functional theory (DFT + vdW) is used to study the effect of pressure up to 20 GPa on the intermolecular interactions of 40 herringbone polycyclic aromatic hydrocarbons. In the first part of this twopart study (10.1021/acs.jpcc.8b07209), we reported the pressure-induced structural changes. Here, we elucidate the relation between those structural changes and the electronic properties, where it is shown that increased pressure leads to variations in the intermolecular interactions and molecular conformations, resulting in alterations of the band dispersion, band gap (magnitude as well as direct/indirect), and semiconductor polarity (n-type vs p-type). Specifically, increased pressure increases the C−H•••π and π•••π interactions, typically leading to increased intermolecular orbital overlap of the frontier molecular orbitals, resulting in increased intermolecular coupling and band dispersion. In general, the increased intermolecular coupling and band dispersion yields decreased band gaps and increased crystalline polarizabilities, although some variation in these trends occur. The majority of structures follow similar trends. However, some exhibit anomalous pressure responses, including switching between n-type and p-type polarity, transitions between direct/indirect gaps, and discontinuities in the pressure-dependent band gap curves.

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High-resolution FTIR study of the para-terphenyl phase transition at high pressure

Cited by 8 publications

References 32 publications

Growth Regulation of Pentacene-Doped p-Terphenyl Crystals on Their Physical Properties for Promising Maser Gain Medium

Growth Regulation of Pentacene-Doped p-Terphenyl Crystals on Their Physical Properties for Promising Maser Gain Medium

Molecular Simulation of the Pressure-Induced Crystallographic Phase Transition of p-Terphenyl

High-Throughput Pressure-Dependent Density Functional Theory Investigation of Herringbone Polycyclic Aromatic Hydrocarbons: Part 2. Pressure-Dependent Electronic Properties

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