Static and dynamic studies on cycloheptanol as two-orientational glass-former

Puertas, R.; Salud, J.; López, David; Rute, M.A.; Díez, Sergio Cañas; Tamarit, J. Ll.; Barrio, Marı́a; Pérez‐Jubindo, M. A.; Fuente, M. R. de la; Pardo, Luis Carlos

doi:10.1016/j.cplett.2004.11.078

Cited by 27 publications

(40 citation statements)

References 22 publications

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“…Such plastic phases are formed from the liquid and can be supercooled, giving rise to the so-called orientational glasses (OG) or "glassy crystals" [6][7][8][9]. They show typically low fragility, as cyclooctanol (m ¼ 33) [10,11], cycloheptanol (m ¼ 22) [12], ortho-carborane (m ¼ 20) [13], cyano-adamantane (m ¼ 17) [9,14], adamantanone (m ≈ 16) [9,15], ethanol (m ¼ 48) [9], or mixed molecular crystals NPA 0.7 NPG 0.3 fðCH 2 OHÞCðCH 3 Þ 3 g 0.7 fðCH 2 OHÞ 2 CðCH 3 Þ 2 g 0.3 (m¼30) [16][17][18]. The most fragile OG known to date are the Freon 112 (CCl 2 F-CCl 2 F) with m ¼ 68 [19] and a co-crystal of succinonitrile (60%) and glutaronitrile (40%) with m ¼ 62 [20].…”

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confidence: 99%

Thermodynamic and Kinetic Fragility of Freon 113: The Most Fragile Plastic Crystal

Vispa¹,

Romanini²,

Ramos

et al. 2017

Phys. Rev. Lett.

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We present a dynamic and thermodynamic study of the orientational glass former Freon 113 (1,1,2-trichloro-1,2,2-trifluoroethane, CCl 2 F-CClF 2 ) in order to analyze its kinetic and thermodynamic fragilities. Freon 113 displays internal molecular degrees of freedom that promote a complex energy landscape. Experimental specific heat and its microscopic origin, the vibrational density of states from inelastic neutron scattering, together with the orientational dynamics obtained by means of dielectric spectroscopy have revealed the highest fragility value, both thermodynamic and kinetic, found for this orientational glass former. The excess in both Debye-reduced specific heat and density of states (boson peak) evidences the existence of glassy low-energy excitations. We demonstrate that early proposed correlations between the boson peak and the Debye specific heat value are elusive as revealed by the clear counterexample of the studied case. DOI: 10.1103/PhysRevLett.118.105701 When a structurally disordered system is rapidly cooled to avoid crystallization, some properties, such as viscosity, show a dramatic increase down to the glass transition where the material reaches viscosity values comparable to those of a solid (10 12 Pa s), i.e., relaxation times of ≈100 s. Such behavior contrasts with that typical for most liquids at high temperatures, which usually exhibit a simple Arrhenius behavior of the relaxation time, τ ¼ τ 0 expðE a =k B TÞ, where the activation energy is temperature independent.Decreasing temperature relaxation time shows a stronger increase, faster than that of the Arrhenius law and accompanied with an increase of some characteristic cooperativity relaxation length. The viscosity (or τ) increase is generally characterized by recourse to the concept of the kinetic fragility [1,2], m ¼ fð∂ log τÞ=½∂ðT g =TÞg T¼T g , which accounts for the deviation of the Arrhenius temperature dependence.In terms of fragility index m, materials for which τ follow an Arrhenius law are known as "strong" glass formers, whereas "fragile" glass formers are those exhibiting super-Arrhenius behavior. For such cases, the temperature dependence of τ is given through the Vogel-FulcherTammann (VFT) expression,where the temperature T 0 is associated with an ideal glass transition and even with the so-called Kauzmann temperature [3], and the fragility strength parameter D is linked to the fragility parameter by. Typical strong glass formers (m ≈ 16, or D ≥ 100) are tetrahedral network liquids as SiO 2 or GeO 2 . The highest values of fragility for organic materials (exception made of polymers) have been found in cis-or trans-decahydronaphthalene (m ¼ 147 [4]). Another group of materials exhibiting glasslike properties is that of crystals with positional order and orientational disorder [5]. Such plastic phases are formed from the liquid and can be supercooled, giving rise to the so-called orientational glasses (OG) or "glassy crystals" [6][7][8][9]. They show typically low fragility, as cyclooctanol (m ¼ 33) [10,11]

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mentioning

confidence: 99%

Thermodynamic and Kinetic Fragility of Freon 113: The Most Fragile Plastic Crystal

Vispa¹,

Romanini²,

Ramos

et al. 2017

Phys. Rev. Lett.

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“…In fact both phases I and II can be supercooled at temperatures below 170 K and only the phase transition from supercooled phase I or II to phase III has been reported to exist, as it can be observed in Fig. 1 of a previous paper [19].…”

Section: Phasementioning

confidence: 87%

“…In the present paper about C 7 -OH, compared to the earlier study of Puertas et al [19], we provide additional dielectric data for supercooled phase II at lower temperatures and, the most important, new dielectric data relating to other stable solid phase(s) at lower temperatures. Unfortunately no new thermal data have been obtained neither for the solid state polymorphism nor for the glassy behavior of the disordered phases.…”

Section: Introductionmentioning

confidence: 86%

“…The heating from 180 K up to the liquid state allows observing a phase transition at about 220 K to a phase with high values of static dielectric permittivity and two other phase transitions at higher temperatures. The vertical dashed lines correspond to the already published phase transition temperatures [19,27] obtained by means of thermal analysis. So, the identification with the stable solid phases I, II and III is rather evident.…”

Section: Phasementioning

confidence: 98%

“…Materials that can be prepared in two different OG-states are far less frequent [19] and if, additionally, they could also be prepared as another class of glass, such materials would be still much rarer.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Solid phases in cycloheptanol: Dynamic disorder and glass transitions

Salud

López

Diez‐Berart

et al. 2009

Journal of Non-Crystalline Solids

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Secondary relaxations of orientationally disordered mixed crystals at temperatures lower than the glass transition temperature

García

Tamarit

Pardo

et al. 2011

Physica Status Solidi (a)

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Low‐molecular weight cyclic alcohols as cycloheptanol (C7H14O, hereinafter referred to as cC7‐ol) and cyclooctanol (C8H16O, cC8‐ol) are prototypical materials displaying OD phases which, under fast cooling give rise to orientational glasses (OG). In addition to the ubiquitous α‐relaxation of canonical glasses, several secondary relaxations appear for the mentioned systems (β and γ for cC8‐ol and β for cC7‐ol). The intramolecular character of these secondary relaxations for these materials as well as their mixed crystals was highlighted at temperatures close but above the glass transition. For lower temperatures the low values of dielectric strength makes difficult to account for the relaxation times obtained from the permittivity losses and, thus in this work we present a data analysis based on the Kramers–Kronig relations which connect the real and imaginary parts of dielectric permittivity and shows up a new method to make evident the existence of such secondary relaxations as well as to avoid phenomenological equations for determining the relaxation time.

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Static and dynamic studies on cycloheptanol as two-orientational glass-former

Cited by 27 publications

References 22 publications

Thermodynamic and Kinetic Fragility of Freon 113: The Most Fragile Plastic Crystal

Thermodynamic and Kinetic Fragility of Freon 113: The Most Fragile Plastic Crystal

Solid phases in cycloheptanol: Dynamic disorder and glass transitions

Secondary relaxations of orientationally disordered mixed crystals at temperatures lower than the glass transition temperature

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