Melting Point and Solid–Liquid Coexistence Properties of α1 Isotactic Polypropylene as Functions of Its Molar Mass: A Molecular Dynamics Study

2016 ◽  
Vol 49 (12) ◽  
pp. 4663-4673 ◽  
Author(s):  
Nikolaos A. Romanos ◽  
Doros N. Theodorou
Keyword(s):  
Molecular Dynamics ◽  
Melting Point ◽  
Isotactic Polypropylene ◽  
Molar Mass ◽  
Solid Liquid

scholarly journals Addressing the discrepancy of finding the equilibrium melting point of silicon using molecular dynamics simulations

2017 ◽  
Vol 473 (2202) ◽  
pp. 20170084 ◽  
Author(s):  
Saeed Zare Chavoshi ◽  
Shuozhi Xu ◽  
Saurav Goel
Keyword(s):  
Molecular Dynamics ◽  
Melting Point ◽  
Molecular Dynamics Simulations ◽  
Interatomic Potential ◽  
Melting Method ◽  
Molecular Systems ◽  
Equilibrium Melting Point ◽  
Wide Range ◽  
Dynamics Simulations ◽  
Solid Liquid

We performed molecular dynamics simulations to study the equilibrium melting point of silicon using (i) the solid–liquid coexistence method and (ii) the Gibbs free energy technique, and compared our novel results with the previously published results obtained from the Monte Carlo (MC) void-nucleated melting method based on the Tersoff-ARK interatomic potential (Agrawal et al. Phys. Rev. B 72 , 125206. ( doi:10.1103/PhysRevB.72.125206 )). Considerable discrepancy was observed (approx. 20%) between the former two methods and the MC void-nucleated melting result, leading us to question the applicability of the empirical MC void-nucleated melting method to study a wide range of atomic and molecular systems. A wider impact of the study is that it highlights the bottleneck of the Tersoff-ARK potential in correctly estimating the melting point of silicon.

Vibrational Contribution to Thermal Conductivity of Silicon Near Solid-Liquid Transition

2011 ◽  
Author(s):  
Christopher H. Baker ◽  
Chengping Wu ◽  
Richard N. Salaway ◽  
Leonid V. Zhigilei ◽  
Pamela M. Norris
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Melting Point ◽  
Silicon Substrates ◽  
Liquid Transition ◽  
Electron Contribution ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
Solid Liquid ◽  
Vibrational Contribution

Although thermal transport in silicon is dominated by phonons in the solid state, electrons also participate as the system approaches, and exceeds, its melting point. Thus, the contribution from both phonons and electrons must be considered in any model for the thermal conductivity, k, of silicon near the melting point. In this paper, equilibrium molecular dynamics simulations measure the vibration mediated thermal conductivity in Stillinger-Weber silicon at temperatures ranging from 1400 to 2000 K — encompassing the solid-liquid phase transition. Non-equilibrium molecular dynamics is also employed as a confirmatory study. The electron contribution may then be estimated by comparing these results to experimental measurements of k. The resulting relationship may provide a guide for the modeling of heat transport under conditions realized in high temperature applications, such as laser irradiation or rapid thermal processing of silicon substrates.

Melting and Crystallization of Poly(oxyethylene) Mixtures

1995 ◽  
Vol 60 (11) ◽  
pp. 1855-1868 ◽  
Author(s):  
Ivo Lapeš ◽  
Josef Baldrian ◽  
Ján Biroš ◽  
Julius Pouchlý ◽  
Hanes Mio
Keyword(s):  
Melting Point ◽  
Lamellar Structure ◽  
Composition Dependence ◽  
Eutectic Phase ◽  
Eutectic Melting ◽  
Pure Polymer ◽  
X Ray ◽  
Long Period ◽  
Solid Liquid ◽  
Melting And Crystallization

Solid-liquid eutectic phase diagrams of mixtures of poly(oxyethylene) (M.w. 2 000) with hydroxy and methoxy endgroups, crystallizing in extended-chain macroconformation only, with glutaric acid, benzoic acid or 1,2-diphenylethane are given. The composition dependence of the melting temperature can be fitted by the Flory-Huggins equation. Interaction parameters X and interaction energy densities B evaluated from the diluent branch of the phase diagram are consistent with those obtained from the polymer branch provided the calorimetric value of enthalpy of polymer fusion is used in the latter computation. Measurements of small- and wide-angle X-ray scatterings showed a stacked lamellar structure of POE. Below the eutectic melting point, the long period of the polymer is almost independent of the diluent concentration. On raising temperature gradually from this melting point to the melting point of pure polymer, the increasing long period indicates the penetration of the diluent between the lamellae. As follows from SAXS measurements, the crystallinity of poly(oxyethylene) in the mixtures remains unchanged compared to that of the pure polymer.

Molecular Dynamics Simulations on Melting of Aluminum

2013 ◽  
Vol 423-426 ◽  
pp. 935-938 ◽  
Author(s):  
Ji Feng Li ◽  
Xiao Ping Zhao ◽  
Jian Liu
Keyword(s):  
Molecular Dynamics ◽  
Melting Point ◽  
Molecular Dynamics Simulations ◽  
High Pressures ◽  
Ambient Pressure ◽  
Initial Porosity ◽  
Equilibrium Melting Point ◽  
Porosity Effect ◽  
Dynamics Simulations ◽  
Experimental Melting Point

Molecular dynamics simulations were performed to calculate the melting points of perfect crystalline aluminum to high pressures. Under ambientpressure, there exhibits about 20% superheating before melting compared to the experimental melting point. Under high pressures, thecalculated melting temperature increases with the pressure but at a decreasing rate, which agrees well with the Simon's melting equation. Porosity effect was also studied for aluminum crystals with various initial porosity at ambient pressure, which shows that the equilibrium melting point decreases with the initial porosity as experiments expect.

On the interface of organic aerosols: molecular level understanding of surface melting, mixing and water adsorption/desorption dynamics

2021 ◽  
Author(s):  
Josip Lovrić ◽  
Xiangrui Kong ◽  
Sofia M. Johansson ◽  
Erik S. Thomson ◽  
Jan B. C. Pettersson
Keyword(s):  
Physical Chemistry ◽  
Molecular Dynamics ◽  
Melting Point ◽  
Molecular Beam ◽  
Molecular Level ◽  
Organic Aerosols ◽  
Md Simulations ◽  
Valeric Acid ◽  
Good Representative ◽  
Hydrophilic Character

<p>The detailed description of organic aerosols surfaces in the atmosphere remains an open issue, which limits our ability to understand and predict environmental change. Important research questions concern the hydrophobic/hydrophilic character of fresh and aged aerosols and the related influence on water uptake in solid, liquid as well in intermediate state.  Also, surface characterization remains big challenge but we find it reachable by conjunction of Molecular Dynamics (MD) simulations and the environmental molecular beam (EMB) experimental method.  A  picture of the detailed molecular-level behavior of water molecules on organic surfaces is beginning to rise based on detailed experimental and theoretical studies; one example is a recent study that investigates water interactions with solid and liquid n-butanol near the melting point [1], another example focus on interaction of water with solid nopinone [2]. From the other side, in order to characterize surface properties during and before melting we employ MD simulations of n-butanol, nopinone and valeric acid. Nopinone (C<sub>9</sub>H<sub>14</sub>O) is a reaction product formed during oxidation of β-pinene and has been found in both the gas and particle phases of atmospheric aerosol. n-butanol (C<sub>4</sub>H<sub>9</sub>OH) is primary alcohol, naturally occurs scarcely and here serves as good representative for alcohols. In the same way valeric acid (CH<sub>3</sub>(CH<sub>2</sub>)<sub>3</sub>COOH) serves as a good representative for a family of carboxylic acids. Valeric acid is, as n-butanol, straight-chain molecule. We show that a classical force field for organic material is able to model crystal and liquid structures. The surface properties near the melting point of the condensed phase are reported, and the hydrophobic and hydrophilic character of the surface layer is discussed.  Overall surface melting dynamic is presented and quantified in the terms of structural and geometrical properties. Mixing of a methanol with the solid nopinone surface is examined and hereby presented.</p><p><strong>References</strong></p><p>[1] Johansson, S. M., Lovrić, J., Kong, X., Thomson, E. S., Papagiannakopoulos, P., Briquez, S., Toubin, C, Pettersson, J. B. C. (2019). Understanding water interactions with organic surfaces: environmental molecular beam and molecular dynamics studies of the water–butanol system. Physical Chemistry Chemical Physics. https://doi.org/10.1039/C8CP04151B   </p><p>[2] Johansson, S. M., Lovrić, J., Kong, X., Thomson, E. S., Hallquist, M., & Pettersson, J. B. C. (2020). Experimental and Computational Study of Molecular Water Interactions with Condensed Nopinone Surfaces Under Atmospherically Relevant Conditions. The Journal of Physical Chemistry A, acs.jpca.9b10970. https://doi.org/10.1021/acs.jpca.9b10970</p><p>Keywords: Molecular Dynamics, organic crystal, organic aerosols, water uptake, surface procesess, molecular level</p>

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