Dynamic characterization of crystalline and glass phases of deuterated 1,1,2,2 tetrachloroethane

Pérez, S.C.; Zuriaga, Mariano; Serra, Pablo; Wolfenson, A. E.; Négrier, Philippe; Tamarit, J. Ll.

doi:10.1063/1.4931824

Cited by 13 publications

(25 citation statements)

References 57 publications

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“…18 This slowest relaxation process (α) corresponds to the cooperative motion associated with the glass-like freezing of the collective molecular motion (i.e., with a glassy transition). 18 The observation of the same relaxation by means of dielectric spectroscopy implies that it is dipolar in character, i.e., it involves a change in the macroscopic polarization of the sample under the applied ac field. It is clear from Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Given that we already identified the ߚ relaxation as the precursor of the primary relaxation, the γ process is not a precursor single-molecule relaxation; moreover, it also cannot be an intramolecular relaxation, because the gauche + conformer is rigid and previous studies have already ruled out the existence of conformational fluctuations in the orthorhombic phase. 15,16,18 In order to identify the exact microscopic origin of the α and γ relaxations, we carried out detailed molecular dynamics simulations in this phase. The molecular structure of the gauche + conformer present in orthorhombic TCE possesses a C 2 symmetry axis orthogonal to the C-C bond and midway between the two carbon atoms.…”

Section: Resultsmentioning

confidence: 99%

“…1(a) that the molecular motion corresponding to the α relaxation can be frozen without transition to a more ordered crystalline phase, i.e., that a glassy state is The activation energy is somewhat lower than that reported for deuterated TCE (41 kJ/mol). 18 The glass transition temperature was calculated as the temperature at which the Arrhenius Eq. 2 gave a value of τ α equal to 100 s. Starting from the fitting parameters of the α relaxation feature, one may employ the so-called Coupling Model (CM) 32 to calculate the relaxation time τ CM of the precursor relaxation associated with the glass transition dynamics, i.e., the characteristic time of the (single-molecule) Johari-Goldstein relaxation.…”

Section: Resultsmentioning

confidence: 99%

“…The intermolecular interactions were described by LennardJones (L-J) and Coulombic potentials 22,23,24,25 (see Ref. 18 for more details).…”

Section: Molecular Simulationsmentioning

confidence: 99%

“…16 Finally, at high pressures (above 0.5 in which all molecules are in the trans conformation. 15 Molecular reorientational dynamics were reported in the orthorhombic phase consisting only of gauche + conformers, where a full assignment of the dynamics was so far not possible, 18 and in the high-pressure monoclinic phase, where the trans conformers undergo rotational motions in which the C-C bond changes its spatial orientation while the chlorine atoms interchange their positions in the crystal structure (in what could be termed a "positional-exchange" reorientation). 19 In this contribution we focus on the orthorhombic phase stable at ambient pressure.…”

Section: Introductionmentioning

confidence: 99%

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Orientational relaxations in solid (1,1,2,2)tetrachloroethane

Tripathi

Mitsari

Romanini

et al. 2016

The Journal of Chemical Physics

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We employ dielectric spectroscopy and molecular dynamic simulations to investigate the dipolar dynamics in the orientationally disordered solid phase of (1,1,2,2)tetrachloroethane. Three distinct orientational dynamics are observed as separate dielectric loss features, all characterized by a simply activated temperature dependence. The slower process, associated to a glassy transition at 156±1 K, corresponds to a cooperative motion by which each molecule rotates by 180º around the molecular symmetry axis through an intermediate state in which the symmetry axis is oriented roughly orthogonally to the initial and final states. Of the other two dipolar relaxations, the intermediate one is the Johari-Goldstein precursor relaxation of the cooperative dynamics, while the fastest process corresponds to an orientational fluctuation of single molecules into a higher-energy orientation. The Kirkwood correlation factor of the cooperative relaxation is of the order of one tenth, indicating that the molecular dipoles maintain on average a strong antiparallel alignment during their collective motion. These findings show that the combination of dielectric spectroscopy and molecular simulations allows studying in great detail the orientational dynamics in molecular solids. 2 INTRODUCTIONWhile conventional (atomic) solids are made of atomic constituents with only translational degrees of freedom, so that their structure is totally determined by translation symmetry and fundamental excitations are vibrational in character, in molecular solids the constituent molecules possess also orientational (as well as internal) degrees of freedom, which lead to a richer variety of possible solid phases and to the existence of rotational excitations such as librations and orientational relaxations. A molecular solid can display complete translational and rotational order, as in a molecular crystal, or complete rototranslational disorder, as in a molecular glass. In between these two extremes, molecular solids also display phases (known as Orientationally disordered (OD) phases are generally formed by relatively small globular molecules such as derivatives of methane, 1,2,3 neopentane, 4 adamantane 5 or fullerene, 6 or by small linear ones such as ethane derivatives 7,8,9 and dinitriles. 10 OD solids exhibit many of the phenomenological features of glass formers, displaying in particular a cooperative rotational motion, called α relaxation, that undergoes a continuous, dramatic slow-down upon cooling, 11,12 leading in some cases to a glass-like 3 transition associated with rotational freezing. 13,14 Contrary to structural glasses, which do not exhibit any long-range order, OD phases are characterized by a translationally ordered structure and can therefore be more thoroughly characterized with the help of methods that exploit the translational symmetry such as Bragg diffraction, lattice models, or solid-state NMR spectroscopy. Even more importantly, since as mentioned OD phases are generally formed by molecular species with a simple structure ...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

“…The intermolecular interactions were described by LennardJones (L-J) and Coulombic potentials 22,23,24,25 (see Ref. 18 for more details).…”

Section: Molecular Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Orientational relaxations in solid (1,1,2,2)tetrachloroethane

Tripathi

Mitsari

Romanini

et al. 2016

The Journal of Chemical Physics

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New Intermediate Polymorph of 1-Fluoro-adamantane and Its Second-Order-like Transition toward the Low Temperature Phase

Yuan

Clevers

Burel

et al. 2017

Crystal Growth & Design

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Phase transitions of 1-fluoro-adamantane have been thoroughly investigated by temperatureresolved second harmonic generation (TR-SHG) and X-ray powder diffraction (XRPD). A new polymorph-an intermediate centrosymmetric phase (MT)-between the known orientationally disordered high temperature phase (HT, F ̅ , Z=4) and low temperature phase (LT, P ̅ , Z=2) was unveiled by TR-SHG. The crystal structure of MT was resolved by XRPD in the P mc (Z=2) space group and it is related to the LT phase in a group-subgroup relation. No evidence of any solid-solid transition between these two phases by differential scanning calorimetry (DSC) or cold-stage microscope could be obtained. Therefore, combing TR-SHG, XRPD, DSC and cold-stage microscope results, a second-order transition mechanism is proposed for MT LT transition. h (β) f w by fitting TR-SHG data to a critical w w. Th b β (0.26) h from XRPD data (0.25).

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Structure and Dynamics of the Crystalline Stable Phase of 2-Chlorothiophene

Romanini

Négrier

Mondieig

et al. 2019

Crystal Growth & Design

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The dynamics of a simple and rigid molecule (2-chlorothiophene) has been studied by means of broadband dielectric spectroscopy (BDS) within the low-temperature stable crystalline phase, whose structure has been determined by means of X-ray powder diffraction (XRPD) measurements. The triclinic P1 structure consists of two molecules per asymmetric unit (Z'=2) with site occupancies 80:20 and 60:40 for each molecule of the asymmetric unit. Such a statistical intrinsic disorder is associated with two dynamical relaxation processes corresponding respectively to out-of-plane relaxations around the C-Cl twofold molecular axis and in-plane reorientational motions as proposed previously (Fujiromi and Oguni, J. Phys. Chem. Solids 1993, 54. 437-612). The XRPD and BDS measurements allow rationalizing published nuclear quadrupole resonance data. We show that only the concurrent use of different experimental techniques provides the answer to a complicate case of orientational molecular dynamics in the solid state.

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Dynamic characterization of crystalline and glass phases of deuterated 1,1,2,2 tetrachloroethane

Cited by 13 publications

References 57 publications

Orientational relaxations in solid (1,1,2,2)tetrachloroethane

Orientational relaxations in solid (1,1,2,2)tetrachloroethane

New Intermediate Polymorph of 1-Fluoro-adamantane and Its Second-Order-like Transition toward the Low Temperature Phase

Structure and Dynamics of the Crystalline Stable Phase of 2-Chlorothiophene

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