Critical assessment of the alleged failure of the Classical Nucleation Theory at low temperatures

Cassar, Daniel R.; Serra, André Hofmeister; Peitl, Oscar; Zanotto, Edgar Dutra

doi:10.1016/j.jnoncrysol.2020.120297

Cited by 27 publications

(32 citation statements)

References 53 publications

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“…Our approach and its results confirm the point of view that the mentioned anomaly can be comprehensively treated in terms of CNT and is a particular realization of even much more complex and intriguing features of crystal nucleation than commonly assumed so far (cf. [ 39 , 40 ]).…”

Section: Discussionmentioning

confidence: 99%

“…Consequently, we have here a situation quite different to the standard situation at isothermal crystallization widely analyzed in CNT, the approach to the ultimate steady-state conditions is not governed here by the time-lag in nucleation but by the relaxation time of the liquid to the metastable equilibrium state (cf. [ 39 , 40 ]). Note that this effect will be even more pronounced if relaxation is described more correctly by stretched exponential relaxation.…”

Section: Implications For the Description Of Crystal Nucleation: Kmentioning

confidence: 99%

“…Two previously performed studies on the CNT-breakdown, partly including results of experiments performed over prolonged times, can be traced in [ 39 , 40 ]. In both studies it was concluded that the above discussed deviations of theoretical steady-state nucleation rates from experimental data for temperatures below the temperature of the maximum steady-state nucleation rates are largely caused by the use of nucleation rate data for processes that have not yet reached the ultimate steady-state at the respective nucleation temperatures.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Glass Transition and Structural Relaxation on Crystal Nucleation: Theoretical Description and Model Analysis

Schmelzer

Тропин

Fokin

et al. 2020

Entropy

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In the application of classical nucleation theory (CNT) and all other theoretical models of crystallization of liquids and glasses it is always assumed that nucleation proceeds only after the supercooled liquid or the glass have completed structural relaxation processes towards the metastable equilibrium state. Only employing such an assumption, the thermodynamic driving force of crystallization and the surface tension can be determined in the way it is commonly performed. The present paper is devoted to the theoretical treatment of a different situation, when nucleation proceeds concomitantly with structural relaxation. To treat the nucleation kinetics theoretically for such cases, we need adequate expressions for the thermodynamic driving force and the surface tension accounting for the contributions caused by the deviation of the supercooled liquid from metastable equilibrium. In the present paper, such relations are derived. They are expressed via deviations of structural order parameters from their equilibrium values. Relaxation processes result in changes of the structural order parameters with time. As a consequence, the thermodynamic driving force and surface tension, and basic characteristics of crystal nucleation, such as the work of critical cluster formation and the steady-state nucleation rate, also become time-dependent. We show that this scenario may be realized in the vicinity and below the glass transition temperature, and it may occur only if diffusion (controlling nucleation) and viscosity (controlling the alpha-relaxation process) in the liquid decouple. Analytical estimates are illustrated and confirmed by numerical computations for a model system. The theory is successfully applied to the interpretation of experimental data. Several further consequences of this newly developed theoretical treatment are discussed in detail. In line with our previous investigations, we reconfirm that only when the characteristic times of structural relaxation are of similar order of magnitude or longer than the characteristic times of crystal nucleation, elastic stresses evolving in nucleation may significantly affect this process. Advancing the methods of theoretical analysis of elastic stress effects on nucleation, for the first time expressions are derived for the dependence of the surface tension of critical crystallites on elastic stresses. As the result, a comprehensive theoretical description of crystal nucleation accounting appropriately for the effects of deviations of the liquid from the metastable states and of relaxation on crystal nucleation of glass-forming liquids, including the effect of simultaneous stress evolution and stress relaxation on nucleation, is now available. As one of its applications, this theoretical treatment provides a new tool for the explanation of the low-temperature anomaly in nucleation in silicate and polymer glasses (the so-called “breakdown” of CNT at temperatures below the temperature of the maximum steady-state nucleation rate). We show that this anomaly results from much more complex features of crystal nucleation in glasses caused by deviations from metastable equilibrium (resulting in changes of the thermodynamic driving force, the surface tension, and the work of critical cluster formation, in the necessity to account of structural relaxation and stress effects) than assumed so far. If these effects are properly accounted for, then CNT appropriately describes both the initial, the intermediate, and the final states of crystal nucleation.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Implications For the Description Of Crystal Nucleation: Kmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effects of Glass Transition and Structural Relaxation on Crystal Nucleation: Theoretical Description and Model Analysis

Schmelzer

Тропин

Fokin

et al. 2020

Entropy

Self Cite

View full text Add to dashboard Cite

show abstract

“…Consequently, we have here a situation quite different to the standard situation at isothermal crystallization widely analyzed in CNT, the approach to steady-state conditions is not governed here by the time-lag in nucleation but by the relaxation time of the liquid to the metastable equilibrium state (cf. [37,38]). Note that this effect will be even more pronounced if relaxation is described more correctly be stretched exponential relaxation.…”

Section: Relaxation and Crystal Nucleation: Numerical Computationsmentioning

confidence: 99%

“…Two previously performed studies on the CNT-breakdown, partly including results of experiments performed over prolonged times, can be traced in [37,38]. In both studies it was concluded that the above discussed deviations of theoretical steady-state nucleation rates from experimental data for temperatures below the temperature of the maximum steady-state nucleation rates are largely caused by the use of nucleation rate data that have not yet reached the ultimate steady-state at the respective nucleation temperatures.…”

Section: Introductionmentioning

confidence: 99%

Effects of Glass Transition and Structural Relaxation on Crystal Nucleation: Theoretical Description and Model Analysis

Schmelzer¹,

Тропин²,

Fokin³

et al. 2020

Preprint

Self Cite

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In the application of classical nucleation theory (CNT) and all other theoretical models of crystallization of liquids and glasses it is always assumed that nucleation proceeds only after the supercooled liquid or the glass have completed structural relaxation processes towards the metastable equilibrium state. Only employing such assumption, the thermodynamic driving force of crystallization and the surface tension can be determined in the way it is commonly performed. The present paper is devoted to the theoretical treatment of a different situation when nucleation proceeds concomitantly with structural relaxation. To treat the nucleation kinetics theoretically for such cases, we need adequate expressions for the thermodynamic driving force and the surface tension accounting for the contributions caused by the deviation of the supercooled liquid from metastable equilibrium. In the present paper, such relations are derived. They are expressed via deviations of structural order parameters from their equilibrium values. Relaxation processes result in changes of the structural order parameters with time. As a consequence, the thermodynamic driving force and surface tension, and basic characteristics of crystal nucleation, such as the work of critical cluster formation and the steady-state nucleation rate, also become time-dependent. We show that this scenario may be realized in the vicinity and below the glass transition temperature, and it may occur only if diffusion (controlling nucleation) and viscosity (controlling the alpha-relaxation process) in the liquid decouple. Analytical estimates are illustrated and confirmed by numerical computations for a model system. The theory is successfully applied to the interpretation of experimental data. Several further consequences of this newly developed theoretical treatment are discussed in detail. In line with our previous investigations, we reconfirm that only when the characteristic times of structural relaxation are of similar order of magnitude or longer than the characteristic times of crystal nucleation, elastic stresses evolving in nucleation may significantly affect this process. Completing the analysis of elastic stress effects, for the first time expressions are derived for the dependence of the surface tension of critical crystallites on elastic stresses. As the result, a comprehensive theoretical description of crystal nucleation accounting appropriately for the effects of deviations of the liquid from the metastable states and of relaxation on crystal nucleation of glass-forming liquids, including the effect of simultaneous stress evolution and stress relaxation on nucleation, is now available. As one if its applications, this theoretical treatment provides a new tool for the explanation of the low-temperature anomaly in nucleation in silicate and polymer glasses (the so-called \breakdown" of CNT at temperatures below the temperature of the maximum steady-state nucleation rate). We show that this anomaly results from much more complex features of crystal nucleation in glasses caused by deviations from metastable equilibrium (resulting in changes of the thermodynamic driving force, the surface tension, and the work of critical cluster formation, in the necessity to account of structural relaxation and stress effects) than assumed so far.

show abstract

Molecular Dynamics ( MD ) Simulations of Bioactive Glasses and Glass‐Ceramics

Montazerian

Wilkinson

Mauro

2022

Bioactive Glasses and Glass‐Ceramics

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Critical assessment of the alleged failure of the Classical Nucleation Theory at low temperatures

Cited by 27 publications

References 53 publications

Effects of Glass Transition and Structural Relaxation on Crystal Nucleation: Theoretical Description and Model Analysis

Effects of Glass Transition and Structural Relaxation on Crystal Nucleation: Theoretical Description and Model Analysis

Effects of Glass Transition and Structural Relaxation on Crystal Nucleation: Theoretical Description and Model Analysis

Molecular Dynamics ( MD ) Simulations of Bioactive Glasses and Glass‐Ceramics

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