Effects on the structure of monolayer and submonolayer fluid nitrogen films by the corrugation in the holding potential of nitrogen molecules

Hansen, Flemming Yssing

doi:10.1063/1.1380372

Cited by 7 publications

(4 citation statements)

References 26 publications

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“…All previous results have been obtained accounting for the surface mediation effect according to the McLachlan theory, ,− which is known to decrease the molecular interaction potential. The question is whether this phenomenon affects the phase transition parameters.…”

Section: Resultsmentioning

confidence: 99%

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From Simulation to Thermodynamics of Orientational Transitions in Molecular Layers: Nitrogen Contact Layer on Solids

2018

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Orientational ordering is a well-known feature of polyatomic molecules in contact layers on solid surfaces. The majority of reported results refer to systems significantly depended on specific fluid–substrate interaction. An example is the nitrogen molecular layer commensurate with the graphite lattice at low temperatures. At the same time, it is instructive to analyze intrinsic thermodynamic properties of the molecular layer stabilized by a smooth substrate surface. In this study the nitrogen molecular layer is modeled by the Monte Carlo method with the emphasis placed on the orientational transition. The quadrupole–quadrupole interaction induces the herringbone orientational ordering which stretches the layer lattice along the glide line. The increase of temperature reduces the deformation, and its disappearance coincides with the transition from long- to short-range order. The magnitude of dispersion and electrostatic forces are always comparable even if the long-range ordering is absent, though the contribution of the latter to the internal energy is less than 17%. A new methodology of analysis of orientational transitions is developed accounting for the anisotropy of electrostatic forces inherent in the long-range orientational arrangement, which allows one to circumvent the problem of very small latent heat of the transition and provides its thermodynamic analysis.

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Section: Resultsmentioning

confidence: 99%

“…The McLachlan scheme for accounting for the effect of surface mediation ,− was also included into the model. For details see ref .…”

Section: Methodsmentioning

confidence: 99%

From Simulation to Thermodynamics of Orientational Transitions in Molecular Layers: Nitrogen Contact Layer on Solids

2018

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“…This is the origin of the "insipient triple point" phenomenon. 1,13,14 In some cases, the surface corrugation causes a commensurate− incommensurate phase transition in the adsorbed molecular layer. 11,13,15,16 Even if the adsorbed monolayer does not form a commensurate structure, the surface corrugation affects the contact layer properties.…”

Section: Introductionmentioning

confidence: 99%

“…In the first case, each atom or molecule of the molecular layer is trapped in a local potential minimum (for example, in the center of the graphite hexagon) enhancing the melting temperature of the layer, sometimes even above the 2D critical temperature. This is the origin of the “insipient triple point” phenomenon. ,, In some cases, the surface corrugation causes a commensurate–incommensurate phase transition in the adsorbed molecular layer. ,,, Even if the adsorbed monolayer does not form a commensurate structure, the surface corrugation affects the contact layer properties. Thus, X-ray measurements show a continuous change of the rotational angle of the crystalline lattice of argon relative to that of graphite in the temperature range 44–50 K .…”

Section: Introductionmentioning

confidence: 99%

Fluid–Solid Phase Transition in Molecular Layers Adsorbed on a Smooth Surface: A New Insight from Molecular Simulations

Ustinov

2018

J. Phys. Chem. C

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Two-dimensional (2D) phase transitions in molecular layers adsorbed on various surfaces have attracted much research attention over the past decades. Special attention is paid to the solidification/melting transition using methods based on molecular simulation techniques. The main research interest is focused on parameters of the liquid–solid or fluid–solid transitions; that is, the pressure, the chemical potential, and the density change. It is implied that the liquid and solid phases coexist like vapor and liquid with a flat interface, and the transition occurs simply via gradual increase of the solid fraction at a constant pressure. However, visualization of the transition based on molecular simulation in a canonical Monte Carlo method in a relatively large simulation cell has shown that the liquid and solid phases form islands in the liquid or “lakes” in the solid of arbitrary size and shape without a distinct interface. For this reason, the aim of this study was a detailed analysis of the 2D phase transition with the emphasis on the properties of the intermediate state between the pure liquid (fluid) and the crystal. Thermodynamically, the transition phase behaves like a two-phase system: when the density changes over a certain range at a specified temperature, the tangential pressure is nearly constant. However, no energy barrier was observed at the transition from the pure liquid or fluid to the intermediate phase. The absence of the van der Waals loop provides a very efficient way to determine parameters of the 2D liquid/fluid–solid transition and the chemical potential of the crystalline phase by a thermodynamic integration or direct evaluation with the kinetic Monte Carlo simulation in a sufficiently large simulation cell. The advantage of this way is that it makes the liquid–solid transition reversible without resorting to any special procedures.

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Effect of solid-like nitrogen contact layers on graphite: anisotropy of tangential pressure and orientational order

Ustinov

2015

Adsorption

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Effects on the structure of monolayer and submonolayer fluid nitrogen films by the corrugation in the holding potential of nitrogen molecules

Cited by 7 publications

References 26 publications

From Simulation to Thermodynamics of Orientational Transitions in Molecular Layers: Nitrogen Contact Layer on Solids

From Simulation to Thermodynamics of Orientational Transitions in Molecular Layers: Nitrogen Contact Layer on Solids

Fluid–Solid Phase Transition in Molecular Layers Adsorbed on a Smooth Surface: A New Insight from Molecular Simulations

Effect of solid-like nitrogen contact layers on graphite: anisotropy of tangential pressure and orientational order

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