Liquid state anomalies and the relationship to the crystalline phase diagram

Fijan, Domagoj; Wilson, Mark

doi:10.1103/physreve.99.010103

Cited by 5 publications

(13 citation statements)

References 59 publications

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“…The values of λ investigated in this work are λ = 18 and 26 (compared to the value for silicon λ = 21) and are chosen to reflect the approximate lower and upper ranges of the parameter λ for which anomalous thermodynamic properties are observed. 30 At these values of λ, we observe some novel interactions between certain thermodynamic anomalies which make these two parameterizations perfect for testing our theoretical predictions. We use molecular dynamics (MD) in the NVT ensemble to generate the required thermodynamic data using LAMMPS 66 with the temperature maintained using Nosé-Hoover thermostats.…”

Section: A Potential Models and Methodsmentioning

confidence: 64%

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The interactions between thermodynamic anomalies

Fijan

Wilson

2019

The Journal of Chemical Physics

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The origin of and interactions between key thermodynamic anomalies are derived and analyzed, as are the interactions with the stability (or cavitation) limits. The conditions for interaction are derived from the underlying thermodynamic relations rather than using the morecommonly applied Taylor expansion method. As a result, we derive a general set of equations that govern the interactions between different lines of thermodynamic anomalies using standard manipulation of thermodynamic equations. The validity of the derivations is investigated by comparing them to numerical simulation data and previous Taylor expansion-based results. Simulations are performed using a modified Stillinger-Weber potential in which the balance of the two-and three-body interactions is varied and which serves to highlight the relationships between the various anomalies. The deeply supercooled regime is explored by employing replica exchange methods. The behavior of the anomalies is considered in terms of previously constructed thermodynamic "scenarios." Based on the newly uncovered interaction schemes, we propose a classification strategy for the thermodynamic anomalies (as first-or second-order) which could be extended to additional related anomalies.

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Section: A Potential Models and Methodsmentioning

confidence: 64%

“…Finally, according to Eq. (30), an analogous argument is valid for the heat capacity anomalies. In addition, we note that both the compressibility and heat capacity anomaly intersection scenarios (with the density anomaly) would change in an analogous manner on swapping the TMD and TminD.…”

Section: Classification Scheme For Anomaliesmentioning

confidence: 85%

The interactions between thermodynamic anomalies

Fijan

Wilson

2019

The Journal of Chemical Physics

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“…Recently, the influence of the tetrahedral repulsion parameter λ in the SW potential on the thermodynamic properties and phase transitions was established. − We performed calculations of the effect of λ on seeded crystallization at one temperature. At T = 915 K, the critical size n * = 286 was obtained with λ = 21.…”

Section: Results and Discussionmentioning

confidence: 99%

Crystal Nucleation Kinetics in Supercooled Germanium: MD Simulations versus Experimental Data

2020

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The validity of the classical nucleation theory (CNT), the most important tool to describe and predict nucleation kinetics in supercooled liquids, has been at stake for almost a century. Here, we carried out comprehensive molecular dynamics simulations of the nucleation kinetics of a fast quenched supercooled germanium using the Stillinger–Weber potential at six temperatures, covering a supercooling range of T/T m = 0.70–0.86, where T m is the equilibrium melting temperature. We used the seeding method to determine the number of particles in the critical crystal nuclei at each supercooling, which yielded n * = 150–1300 atoms. The transport coefficient at the liquid/nucleus interface and the melting point were also obtained from the simulations. Using the parameters resulting directly from the simulations, the CNT embraces the experimental nucleation rates, J(T), with the following fitted (average) values of the nucleus/liquid interfacial free energy: γ = 0.244 and 0.201 J/m2, for the experimental and calculated values of thermodynamic driving force, Δμ(T), respectively, which are close to the value obtained from n *(T). Without using any fit parameter, the calculated nucleation rates for the experimental and calculated values of Δμ(T) embrace the experimental J(T) curve. Therefore, this finding favors the validity of the CNT.

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“…This gives a characteristic 'S' shape to both compressibility anomalies as can be seen in figure 1(b). At lower values of λ = 18, the TMC and TminC loci may merge at high pressure [29], while high values of λ = 27 the anomalies weaken and the 'S' shape of the TminC locus is replaced by a line with only positive gradient in the pT projection [30,51]. A similar progression has been found in models for BeF 2 in which the anion polariability is used as a free parameter (in the analogue of the use of the SW λ parameter) [52].…”

Section: The Thermodynamic Anomaliesmentioning

confidence: 99%

“…Recent theoretical and computational work has focussed on two key aspects regarding these anomalies. In one case work has focussed on mapping how the anomalies shift in phase space as a potential model is systematically modified [30]. In the second case the mathematical constraints, which govern how these anomalies may intersect and interact with each other and stability limits, have been studied [29].…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic anomalies in silicon and the relationship to the phase diagram

Fijan

Wilson

2021

J. Phys.: Condens. Matter

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The evolution of thermodynamic anomalies are investigated in the pressure–temperature (pT) plane for silicon using the well-established Stillinger–Weber potential. Anomalies are observed in the density, compressibility and heat capacity. The relationships between them and with the liquid stability limit are investigated and related to the known thermodynamic constraints. The investigations are extended into the deeply supercooled regime using replica exchange techniques. Thermodynamic arguments are presented to justify the extension to low temperature, although a region of phase space is found to remain inaccessible due to unsuppressible crystallisation. The locus corresponding to the temperature of minimum compressibility is shown to display a characteristic ‘S’-shape in the pT projection which appears correlated with the underlying crystalline phase diagram. The progression of the anomalies is compared to the known underlying phase diagrams for both the crystal/liquid and amorphous/liquid states. The locations of the anomalies are also compared to those obtained from previous simulation work and (limited) experimental observations.

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Liquid state anomalies and the relationship to the crystalline phase diagram

Cited by 5 publications

References 59 publications

The interactions between thermodynamic anomalies

The interactions between thermodynamic anomalies

Crystal Nucleation Kinetics in Supercooled Germanium: MD Simulations versus Experimental Data

Thermodynamic anomalies in silicon and the relationship to the phase diagram

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