Simulated pressure response of crystalline indole

Schatschneider, Christopher; Liang, Jing

doi:10.1063/1.3655466

Cited by 16 publications

(32 citation statements)

References 39 publications

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“…23 These two points lead to the fact that most highpressure studies cannot obtain the unique behaviors of faceto-face π -stacking. [24][25][26][27][28] Therefore, the high-pressure exploration of face-to-face π -stacking is far from complete.…”

Section: Introductionmentioning

confidence: 99%

Compression studies of face-to-face π-stacking interaction in sodium squarate salts: Na2C4O4 and Na2C4O4•3H2O

Wang

et al. 2012

The Journal of Chemical Physics

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High-pressure Raman scattering and synchrotron X-ray diffraction measurements of sodium squarate (Na(2)C(4)O(4), SS) are performed in a diamond anvil cell. SS possesses a rare, but typical structure, which can show the effect of face-to-face π-stacking without interference of other interactions. At ~11 GPa, it undergoes a phase transition, identified as a symmetry transformation from P2(1)/c to P2(1). From high-pressure Raman patterns and the calculated model of SS, it can be proved that the phase transition results from the distorted squarate rings. We infer it is the enhancement of π-stacking that dominates the distortion. For comparison, high-pressure Raman spectra of sodium squarate trihydrate (Na(2)C(4)O(4)●3H(2)O, SST) are also investigated. The structure of SST is determined by both face-to-face π-stacking and hydrogen bonding. SST can be regarded as a deformation of SS. A phase transition, with the similar mechanism as SS, is observed at ~10.3 GPa. Our results can be well supported by the previous high-pressure studies of ammonium squarate ((NH(4))(2)C(4)O(4), AS), and vice versa. High-pressure behaviors of the noncovalent interactions in SS, SST, and AS are compared to show the impacts of hydrogen bonding and the role of electrostatic interaction in releasing process.

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Section: Introductionmentioning

confidence: 99%

Compression studies of face-to-face π-stacking interaction in sodium squarate salts: Na2C4O4 and Na2C4O4•3H2O

Wang

et al. 2012

The Journal of Chemical Physics

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“…The use of a relatively high plane wave basis set cutoff is to ensure that the total energy and unit cell volume converge, as demonstrated in a similar study of crystalline indole. 31 The k-point grid was kept to maintain a spacing of ca. 0.07 Å 21 .…”

Section: Computational Detailsmentioning

confidence: 99%

Phase transition between cubic and monoclinic polymorphs of the tetracyanoethylene crystal: the role of temperature and kinetics

Schatschneider

Liang²,

Jezowski

et al. 2012

CrystEngComm

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Prediction of the relative stabilities and phase transition behavior of molecular crystalline polymorphs is highly coveted as distinct phases can possess different physical and chemical properties while having similar energies. Crystalline tetracyanoethylene (TCNE, C 6 N 4 ) is known to exhibit rich solid state phase behavior under different thermodynamic conditions, as demonstrated by a wealth of experimental studies on this system. Despite this fact, the role of temperature and kinetics on the phase diagram of TCNE remains poorly understood. Here, first-principles calculations and highresolution Fourier-transformed infrared (HR-FTIR) spectroscopy experiments are used to study the relative stabilities of the cubic and monoclinic phases of TCNE as a function of temperature. Specifically, density-functional theory with the van der Waals interactions method of Tkatchenko and Scheffler (DFT+vdW) is employed. The accuracy of this approach is demonstrated by the excellent agreement between the calculated and experimental structures. We find that the cubic phase is the most stable polymorph at 0 K, but becomes less favorable than the monoclinic phase at 160 K. This temperature-induced phase transition is explained on the basis of varying close contacts and vibrational entropies as a function of temperature. These findings are supported by a temperaturedependent HR-FTIR linewidth study of the CMN vibrons.

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“…The plane-wave basis set cutoff was set to 750 eV, ensuring that the total energy and unit cell volume were converged, as demonstrated in the study of crystalline indole and tetracyanoethylene. 23,24 The k-point grid was kept to maintain a spacing of 0.07Å −1 . Explicit all-electron calculations using the FHI-aims code 25 confirm that the binding energies from the pseudopotential calculations are converged to better than 0.01 eV per molecule.…”

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confidence: 99%

Electrodynamic response and stability of molecular crystals

Schatschneider

Liang²,

Reilly

et al. 2013

Phys. Rev. B

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We show that electrodynamic dipolar interactions, responsible for long-range fluctuations in matter, play a significant role in the stability of molecular crystals. Density functional theory calculations with van der Waals interactions determined from a semilocal "atom-in-a-molecule" model result in a large overestimation of the dielectric constants and sublimation enthalpies for polyacene crystals from naphthalene to pentacene, whereas an accurate treatment of nonlocal electrodynamic response leads to an agreement with the measured values for both quantities. Our findings suggest that collective response effects play a substantial role not only for optical excitations, but also for cohesive properties of noncovalently bound molecular crystals. Polyacene molecular crystals form a fundamental class of aromatic solids, and have been extensively studied as potential materials for organic electronics. [1][2][3] It is understood that the optical properties of polyacenes are very sensitive to longrange intra-and intermolecular electrodynamic interactions. This is reflected by shifts in the optical absorption frequencies upon increasing the molecule size or upon solid formation, 4 and is further exhibited by the visible color of oligoacene crystals, which changes from transparent in naphthalene and anthracene, to bright orange in tetracene, and deep blue in pentacene. 4,5 The optical absorption spectrum is directly related to the polarizability through the Kramers-Kronig transformation.6 Therefore, the observed changes in the optical spectrum upon crystallization of polyacenes are accompanied by a change in the molecular polarizability. In addition, these changes in polarization should directly impact the crystal lattice energy. However, the effect of electrodynamic intermolecular interactions on the cohesive properties of molecular crystals remains poorly understood. In this Rapid Communication, we show that the dipolar electrodynamic coupling between polyacene molecules reduces the solid dielectric constant by 15%, and has an impact of up to 0.5 eV per molecule on the computed van der Waals (vdW) energies and sublimation enthalpies of these molecular crystals. Our results imply that electrodynamic response is crucial for describing both the cohesive energy and the optical properties of molecular crystals, also providing strong quantitative support to empirical relations between stability and refractive index of molecular crystals. 7Polyacene crystals are extended aromatic networks characterized by polarizable π clouds. Therefore, an appreciable part of the crystal lattice energy stems from ubiquitous attractive vdW dispersion interactions. When studying the cohesion of molecular systems, for example, using densityfunctional theory (DFT) 8,9 or classical potentials, 10 the vdW energy is typically computed using effective polarizabilities for hybridized "atoms" inside a molecule. It is common to approximate the frequency-dependent polarizability of every atom using a single effective excitation frequency (also called t...

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Simulated pressure response of crystalline indole

Cited by 16 publications

References 39 publications

Compression studies of face-to-face π-stacking interaction in sodium squarate salts: Na2C4O4 and Na2C4O4•3H2O

Compression studies of face-to-face π-stacking interaction in sodium squarate salts: Na2C4O4 and Na2C4O4•3H2O

Phase transition between cubic and monoclinic polymorphs of the tetracyanoethylene crystal: the role of temperature and kinetics

Electrodynamic response and stability of molecular crystals

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