Dielectric properties of liquid ethanol. A computer simulation study

Saiz, Leonor; Guàrdia, E.; Padró, Joan-Àngel

doi:10.1063/1.1305883

Cited by 77 publications

(64 citation statements)

References 39 publications

(46 reference statements)

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“…It was shown that an enhancement of the dynamics occurs when the number of cross-links decreases and consequently the network becomes looser. Because of its inherent dynamic nature, the hydrogen-bond network in primary alcohols is more complex [17,18] than in standard polymer networks. However, the increment of F II max with crystallinity can be interpreted consistently as being due to a depletion of relaxing species from the hydrogenbond network.…”

Section: Fig 3 (Color Online)mentioning

confidence: 99%

Hydrogen-Bond Network Breakage as a First Step to Isopropanol Crystallization

et al. 2004

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Here we present an experimental study of isopropanol crystallization in real time by means of a novel setup combining simultaneously structural measurements with dynamical techniques. By coupling time resolved neutron diffraction and dielectric spectroscopy experiments we demonstrate that a breakage of the hydrogen-bond network is a precursor step for the crystallization of isopropanol. DOI: 10.1103/PhysRevLett.93.015503 PACS numbers: 61.12.Ex, 61.20.Lc, 77.22.-d Upon cooling liquids may either crystallize or vitrify. Crystallization is a common phase transition by which molecules self-organize into crystals [1]. Water is one of the most important liquids due to its direct implication in life. Among the peculiarities of liquid water is the presence of a dynamic three-dimensional hydrogen-bond network [2 -4]. The physical and chemical properties of hydrogen-bond network forming liquids are controlled by the extension of intermolecular structures resulting from hydrogen bonds [5,6]. Related to crystallization, molecular dynamics simulation in water indicated that crystal nucleation occurs after a significant reorganization of the hydrogen-bond network [4]. However, this network modification has not been observed experimentally. This is in part due to the fast freezing kinetics of water [4]. On the contrary, crystallization kinetics of isopropanol, which is also a hydrogen-bond network forming liquid, can be thermally controlled from hours to seconds [7]. The major problem to correlate the evolution of a dynamic magnitude with that of a structural one comes from simultaneity. Crystallization phenomena can be very well studied by diffraction or calorimetry, among others. The dynamics of the hydrogen-bond network can be also well characterized by means of relaxation techniques such as dielectric spectroscopy [8,9]. However, in order to find a direct relationship between structure and dynamics, simultaneity may be crucial. Our experiments involve a novel experimental setup which allows one to perform simultaneous measurements of time resolved neutron diffraction (ND) and dielectric spectroscopy (DS). DS measures the complex dielectric permittivity " " 0 ÿ i" 00 as a function of frequency, where " 0 is the dielectric constant and " 00 is the dielectric loss. By measuring as a function of temperature, dielectric spectroscopy becomes a very powerful method to study molecular dynamics in liquids [8][9][10] above the glass transition temperature T g . In this case, molecular motions give rise to a characteristic relaxation process, which can be observed as a maximum [8][9][10] in " 00 . To perform simultaneously ND measurements we have designed a special sample holder made from insulating anodized aluminum.Inside the container the liquid is placed between two standard aluminum pieces acting as electrodes separated by two Teflon  spacers and are connected to a Stanford lock-in amplifier SR830 with a dielectric interphase and control unit from Novocontrol. The cell is incorporated into an ILL orange cryostat specially d...

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Section: Fig 3 (Color Online)mentioning

confidence: 99%

Hydrogen-Bond Network Breakage as a First Step to Isopropanol Crystallization

et al. 2004

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“…With respect to the employed HB criterion, six different bonding states are possible; the fractions of molecules in different bonding states can be represented by a 3 × 2m a t r i xξ , for the elements of which we use notation ξ i d ,j a where i d = (0, 1, or 2) is the number of donor molecules bonded to the molecules and j a = (0 or 1) is the number of its acceptors. The relation between ξ i d ,i a and the fraction of molecules with m H-bonds f m (which is used in classical works 27,68 ) is straightforward:…”

Section: Technical Detailsmentioning

confidence: 99%

Size distribution of associated clusters in liquid alcohols: Interpretation of simulation results in the frame of SAFT approach

Janeček

Paricaud

2013

The Journal of Chemical Physics

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The size distribution and topology of associated clusters for primary alcohols is studied using molecular dynamics simulations. Liquid ethanol, propanol, butanol, hexanol, and octanol are simulated at pressure P = 1 bar and temperatures T = 300 K, T = 350 K, and T = 400 K. The fractions of molecules with different sets of hydrogen bonded partners, the size of associated cluster and the site-site distribution functions between atoms participating on hydrogen bonding are extracted from simulated trajectories. For all alcohols longer than ethanol, the length of the alkyl chain has only a marginal effect on the association. Consequently, related properties like coordination numbers of hydroxyl group, size distribution of associates, or fractions of differently coordinated alcohol molecules are independent on the molecular size. Although we employed a force-field without involved polarizability, we observe a positive cooperativity of hydrogen bonding simply as a consequence of steric and electrostatic interactions. The size and topology of associates is analyzed within the frame of 3B model of statistical association fluid theory. Although this approach enables good thermodynamic description of systems containing associating compounds, several insufficiencies appear in the description at molecular level. © 2013 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4827107]

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“…A similar behaviour is apparent in Φ s (t). They are probably a signature of the librational dynamics associated with the existence of HB, as suggested in previous simulations of ethanol [12]. The long time decay of both functions cannot be properly modelled by exponentials, and they are best fit with stretched exponential functions (Φ s (t) = Aexp(−(t/τ 1 ) β 1 ) and Φ(t) = Aexp(−(t/τ Φ ) β Φ ), respectively).…”

Section: Dynamic Dielectric Propertiesmentioning

confidence: 99%

“…The finite system Kirkwood factor has been evaluated in our simulations by means of equation (12). Its values are gathered in table II, as well as the ones for the permittivity and the infinite system Kirwook factor, which have been obtained by using equations (11) and (13) respectively.…”

Section: Static Dielectric Propertiesmentioning

confidence: 99%

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Influence of hydrogen bonds and temperature on dielectric properties

Urbina

Sesé

2016

Phys. Rev. E

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Dielectric properties have been evaluated by means of Molecular Dynamics simulations on two model systems made up by dipolar molecules. One of them mimics methanol, whereas the other differs from the former only in the ability of forming hydrogen bonds. Static dielectric properties such as permittivity and the Kirkwood factor have been evaluated, and results have been analyzed by considering the distribution of relative orientations between molecular dipoles. Dipole moment time correlation functions have also been evaluated. The relevance of contributions associated to autocorrelations of molecular dipoles and to cross-correlations between dipoles belonging to different molecules has been investigated. For methanol, the Debye approximation for the overall dipole moment correlation function is not valid at room temperature. The model applies when hydrogen bonds are suppressed, but it fails upon cooling the non-associated liquid. Important differences between relaxation times associated with dipole auto and cross-correlations as well as their relative relevance are at the root of the Debye model breakdown. *

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Dielectric properties of liquid ethanol. A computer simulation study

Cited by 77 publications

References 39 publications

Hydrogen-Bond Network Breakage as a First Step to Isopropanol Crystallization

Hydrogen-Bond Network Breakage as a First Step to Isopropanol Crystallization

Size distribution of associated clusters in liquid alcohols: Interpretation of simulation results in the frame of SAFT approach

Influence of hydrogen bonds and temperature on dielectric properties

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