Melting in two-dimensional systems: Characterizing continuous and first-order transitions

Toledano, Óscar; Pancorbo, Manuel; Alvarellos, J. E.; Gálvez, Óscar

doi:10.1103/physrevb.103.094107

Cited by 10 publications

(4 citation statements)

References 43 publications

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“…Cut-off functions, commonly employed in various models, play a crucial role in ne-tuning short-and long-range interactions among atoms. 29 We implemented the function f c (r) de ned by parameters r, r max , and r min , ensuring its rst and second derivatives are zero at both ending positions for the sake of stable simulations. We set r min =3.0 Å in all the simulations.…”

Section: Resultsmentioning

confidence: 99%

Temperature and Degrees of Freedom of Potential Energy vs Its Kinetic Counterparts and Their Roles in Decoding Phase Transition

Zou,

Wang

2024

Preprint

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Temperature, a fundamental metric in thermal energy characterization, encounters intriguing exceptions during phase transitions, where it maintains a constant value despite significant internal energy alterations. Equipartition theorem also failed in interpreting these phenomena. In this study, we introduce a novel framework termed "potential energy temperature (Tpot)" and associated degrees of freedom (Dpot) to provide deeper insights into phase transitions. Our investigations reveal that Tpot diverges considerably from conventional temperature (Tkin) defined by kinetic energy, and Dpot is influenced not only by dimensions in Cartesian coordinate but also by the number of interacting atoms. A noteworthy finding is the correlation between phase changes and increased Dpot, which explains the observed increase in potential energy using the equipartition theorem. Additionally, we identify a sudden change in Tpot during the phase transition, diverging from conventional descriptions. Furthermore, our study unveils unconventional concepts, such as the potential energy of an atom being significantly lower at higher temperatures than at absolute zero. These findings offer a fresh perspective on the phase changes of matter, challenging existing paradigms and providing insights into this complex yet fundamental natural process.

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Section: Resultsmentioning

confidence: 99%

Temperature and Degrees of Freedom of Potential Energy vs Its Kinetic Counterparts and Their Roles in Decoding Phase Transition

Zou,

Wang

2024

Preprint

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“…Nevertheless, there is evidence of a weak and range-limited pre-melting effect on heating from the solid phase. The basic model explanation suggests the fragmentation of the solid into crystalline grains covered by quasi-liquid nanolayers [ 46 , 59 , 60 , 61 , 62 , 63 ]. However, the volume associated with these nano-layers is (very) minimal compared to the volume occupied by solid, crystalline grains.…”

Section: Resultsmentioning

confidence: 99%

The Dominance of Pretransitional Effects in Liquid Crystal-Based Nanocolloids: Nematogenic 4-methoxybenzylidene-4′–butylaniline with Transverse Permanent Dipole Moment and BaTiO3 Nanoparticles

Drozd-Rzoska,

Łoś,

Rzoska

2024

Nanomaterials

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The report presents static, low-frequency, and dynamic dielectric properties in the isotropic liquid, nematic, and solid phases of MBBA and related nanocolloids with paraelectric BaTiO3 nanoparticles (spherical, d = 50 nm). MBBA (4-methoxybenzylidene-4′–butylaniline) is a liquid crystalline compound with a permanent dipole moment transverse to the long molecular axis. The distortions-sensitive analysis of the dielectric constant revealed its hidden pretransitional anomaly, strongly influenced by the addition of nanoparticles. The evolution of the dielectric constant in the nematic phase shows the split into two regions, with the crossover coinciding with the standard melting temperature. The ‘universal’ exponential-type behavior of the low-frequency contribution to the real part of the dielectric permittivity is found. The critical-like pretransitional behavior in the solid phase is also evidenced. This is explained by linking the Lipovsky model to the Mossotti catastrophe concept under quasi-negative pressure conditions. The explicit preference for the ‘critical-like’ evolution of the apparent activation enthalpy is worth stressing for dynamics. Finally, the long-range, ‘critical-like’ behavior of the dissipation factor (D = tgδ), covering the isotropic liquid and nematic phases, is shown.

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“…For soft Morse interactions, the third melting scenario was observed for all temperatures considered in Ref. 46 , whereas the authors expected to observe the BKTHNY scenario at higher temperatures. However, at some parameters of potential softness, two continuous transitions were observed already at low temperatures in the presence of long-range attraction.…”

Section: Introductionmentioning

confidence: 88%

“…LJ crystals compared with the Morse system in Ref. 46 were shown to melt via the third scenario at low temperatures and two continuous BKT transitions at high. This agrees with Ref.…”

Section: Introductionmentioning

confidence: 94%

The role of attraction in the phase diagrams and melting scenarios of generalized 2D Lennard-Jones systems

Tsiok,

Fomin,

Gaiduk

et al. 2021

Preprint

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Monolayer and two-dimensional (2D) systems exhibit rich phase behavior, compared with 3D systems, in particular, due to the hexatic phase playing a central role in melting scenarios. The attraction range is known to affect critical gas-liquid behavior (liquid-liquid in protein and colloidal systems), but the effect of attraction on melting in 2D systems remains unstudied systematically. Here, we reveal how the attraction range affects the phase diagrams and melting scenarios in a 2D system. Using molecular dynamics simulations we considered the generalized Lennard-Jones system with a fixed repulsion branch and different power indices of attraction, from long-range dipolar to short-range sticky-spheres-like. A drop in the attraction range has been found to reduce the temperature of the gas-liquid critical point, bringing it closer to the gas-liquid-solid triple point. At high-temperatures, attraction does not affect the melting scenario that proceeds through the cascade of solid-hexatic (Berezinski-Kosterlitz-Thouless) and hexatic-liquid (first-order) phase transitions. In the case of dipolar attraction, we observed two triple points, inherent in a 2D system: hexatic-liquid-gas and crystal-hexatic-gas, the temperature of the crystal-hexatic-gas triple point is below the hexatic-liquid-gas triple point. This observation may have far-reaching consequences for future studies, since phase diagrams determine possible routes of self-assembly in molecular, protein, and colloidal systems, whereas the attraction range can be adjusted with complex solvents and external electric or magnetic fields. The results obtained may be widely used in condensed matter, chemical physics, materials science, and soft matter.

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Melting in two-dimensional systems: Characterizing continuous and first-order transitions

Cited by 10 publications

References 43 publications

Temperature and Degrees of Freedom of Potential Energy vs Its Kinetic Counterparts and Their Roles in Decoding Phase Transition

Temperature and Degrees of Freedom of Potential Energy vs Its Kinetic Counterparts and Their Roles in Decoding Phase Transition

The Dominance of Pretransitional Effects in Liquid Crystal-Based Nanocolloids: Nematogenic 4-methoxybenzylidene-4′–butylaniline with Transverse Permanent Dipole Moment and BaTiO3 Nanoparticles

The role of attraction in the phase diagrams and melting scenarios of generalized 2D Lennard-Jones systems

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