A model for diffusive systems: Beyond the Arrhenius mechanism

Rosa, A. C. P.; Vaveliuk, Pablo; Mundim, Kleber C.; Moret, Marcelo A.

doi:10.1016/j.physa.2015.12.122

Cited by 10 publications

(8 citation statements)

References 44 publications

(58 reference statements)

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“…5(a–f)) for H = 6.8 Å. Such super-Arrhenius behaviour has been found in bulk supercooled liquids 25 and binary Lennard Jones mixtures 26 . Also, NMR and quasielastic neutron scattering study revealed a similar Arrhenius (strong) to super-Arrhenius (fragile) crossover for supercooled confined water 27 .…”

Section: Resultsmentioning

confidence: 52%

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Frenkel line crossover of confined supercritical fluids

Ghosh

Krishnamurthy

2019

Sci Rep

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We investigate the temperature evolution of dynamics and structure of partially confined Lennard Jones (LJ) fluids in supercritical phase along an isobaric line in the P-T phase diagram using molecular dynamics simulations. We compare the Frenkel line (FL) crossover features of partially confined LJ fluids to that of the bulk LJ fluids in supercritical phase. Five different spacings have been chosen in this study and the FL crossover characteristics have been monitored for each of these spacings for temperatures ranging from 240 K to 1500 K keeping the pressure fixed at 5000 bar. We characterize the FL crossover using density of states (DoS) function and find that partially confined supercritical fluids (SCF) exhibit a progressive shift of FL crossover point to higher temperatures for smaller spacings. While the DoS perpendicular to the walls shows persistent oscillatory modes, the parallel component exhibits a smooth crossover from an oscillatory to non-oscillatory characteristics representative of FL crossover. We find that the vanishing of peaks in DoS parallel to the walls indicates that the SCF no longer supports shear mode excitations and could serve as an identifier of the FL crossover for confined systems just as is done for the bulk. Layer heights of density profiles, self-diffusivity and the peak heights of radial distribution function parallel to the walls also feature the FL crossover consistent with the DoS criteria. Surprisingly, self-diffusivity undergoes an Arrhenius to super-Arrhenius crossover at low temperatures for smaller spacings as a result of enhanced structural order evidenced via pair-excess entropy. This feature, typical of glass-forming liquids and binary supercooled liquids, is found to develop from the glass-like characteristic slowdown and strong caging in confined supercritical fluid, evidenced via mean squared displacement and velocity autocorrelation function respectively, over intermediate timescales.

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Section: Resultsmentioning

confidence: 52%

“…The super-Arrhenius diffusion is characterized by a convex-shaped variation of D as a function of temperature 25,28 . From our earlier work 8 , we recall that glass-like behavior was emerging over intermediate timescales in a confined SCF with narrow spacing at room temperature (300 K), giving rise to a small D over long timescales.…”

Section: Resultsmentioning

confidence: 99%

Frenkel line crossover of confined supercritical fluids

Ghosh

Krishnamurthy

2019

Sci Rep

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“…As discussed in this article the approach turns out to be a powerful tool, capable of establishing a connection between canonical data and microcanonical information, permitting comparisons among apparently uncorrelated formulations: it also allows interpretation of empirical parameters, for example for the AM, ASCC, VFT and NTS formulas considered in this paper. Previous (Tsallis and Bukman, 1996; Lenzi et al, 2001; JiangLin et al, 2006; Zhou and Du, 2013) and concomitant (Zhou and Du, 2014; Guo and Du, 2015; Rosa et al, 2016; Junior et al, 2019) efforts have been dedicated to provide also a connection of anomalous kinetic diffusion effects while surmounting a potential barrier via variants of Fokker-Planck equation, tackling a class of phenomenologically physicochemical diffusion process.…”

Section: Additional and Final Remarksmentioning

confidence: 99%

Temperature Dependence of Rate Processes Beyond Arrhenius and Eyring: Activation and Transitivity

2019

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Advances in the understanding of the dependence of reaction rates from temperature, as motivated from progress in experiments and theoretical tools (e. g., molecular dynamics), are needed for the modeling of extreme environmental conditions (e.g., in astrochemistry and in the chemistry of plasmas). While investigating statistical mechanics perspectives (Aquilanti et al., 2017b , 2018 ), the concept of transitivity was introduced as a measure for the propensity for a reaction to occur. The Transitivity plot is here defined as the reciprocal of the apparent activation energy vs. reciprocal absolute temperature. Since the transitivity function regulates transit in physicochemical transformations, not necessarily involving reference to transition-state hypothesis of Eyring, an extended version is here proposed to cope with general types of transformations. The transitivity plot permits a representation where deviations from Arrhenius behavior are given a geometrical meaning and make explicit a positive or negative linear dependence of transitivity for sub - and super -Arrhenius cases, respectively. To first-order in reciprocal temperature, the transitivity function models deviations from linearity in Arrhenius plots as originally proposed by Aquilanti and Mundim: when deviations are increasingly larger, other phenomenological formulas, such as Vogel-Fulcher-Tammann, Nakamura-Takayanagi-Sato, and Aquilanti-Sanches-Coutinho-Carvalho are here rediscussed from the transitivity concept perspective and with in a general context. Emphasized is the interest of introducing into this context modifications to a very successful tool of theoretical kinetics, Eyring's Transition-State Theory: considering the behavior of the transitivity function at low temperatures, in order to describe deviation from Arrhenius behavior under the quantum tunneling regime, a “ d -TST” formulation was previously introduced (Carvalho-Silva et al., 2017 ). In this paper, a special attention is dedicated to a derivation of the temperature dependence of viscosity, making explicit reference to feature of the transitivity function, which in this case generally exhibits a super -Arrhenius behavior. This is of relevance also for advantages of using the transitivity function for diffusion-controlled phenomena.

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“…The mechanism involved in convex curvature of Arrhenius plots in supercooled liquids is one of the less understood unsolved processes in condensed matter science [58,69,70]. An interesting example is the diffusion of krypton in methanol and ethanol mixtures at low temperature near their glass transition temperatures [71][72][73] liquids with different composition exhibit variations of the temperature-dependent viscosity [75]. Around T g temperature, the Arrhenius-like formulation,…”

Section: (A) Super-arrheniusmentioning

confidence: 99%

Kinetics of low-temperature transitions and a reaction rate theory from non-equilibrium distributions

Aquilanti

Coutinho

Carvalho-Silva

2017

Phil. Trans. R. Soc. A.

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relaxing the thermodynamic equilibrium limit, either for a binomial distribution if d > 0 or for a negative binomial distribution if d < 0, formally corresponding to Fermionlike or Boson-like statistics, respectively. The current status of the phenomenology is illustrated emphasizing case studies; specifically (i) the super-Arrhenius kinetics, where transport phenomena accelerate processes as the temperature increases; (ii) the sub-Arrhenius kinetics, where quantum mechanical tunnelling propitiates low-temperature reactivity; (iii) the anti-Arrhenius kinetics, where processes with no energetic obstacles are rate-limited by molecular reorientation requirements. Particular attention is given for case (i) to the treatment of diffusion and viscosity, for case (ii) to formulation of a transition rate theory for chemical kinetics including quantum mechanical tunnelling, and for case (iii) to the stereodirectional specificity of the dynamics of reactions strongly hindered by the increase of temperature.This article is part of the themed issue 'Theoretical and computational studies of nonequilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces'.

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A model for diffusive systems: Beyond the Arrhenius mechanism

Cited by 10 publications

References 44 publications

Frenkel line crossover of confined supercritical fluids

Frenkel line crossover of confined supercritical fluids

Temperature Dependence of Rate Processes Beyond Arrhenius and Eyring: Activation and Transitivity

Kinetics of low-temperature transitions and a reaction rate theory from non-equilibrium distributions

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