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Главная Архив Thermal Letter Оргкомитет Будущие конференции AIHTC
International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Prediction of Anisotropic Crystal-Melt Interfacial Free Energy of Sugar Alcohols Through Molecular Simulations

Huaichen Zhang
Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven, The Netherlands

Silvia V. Nedea
Eindhoven University of Technology, Department of Mechanical Engineering, P.O.Box 513, 5600MB Eindhoven, The Netherlands

Camilo C. M. Rindt
Eindhoven University of Technology, Department of Mechanical Engineering, P.O.Box 513, 5600MB Eindhoven, The Netherlands

Herbert A. Zondag
Eindhoven University of Technology, Department of Mechanical Engineering, P.O.Box 513, 5600MB Eindhoven; ECN, Energy Research Centre of the Netherlands, P.O. Box 1, 1755 ZG Petten, The Netherlands

David M. J. Smeulders
Engineering Thermodynamics for Energy Systems, Department of Mechanical Engineering, Eindhoven University of Technology, Den Dolech 2, 5612AZ Eindhoven, The Netherlands

DOI: 10.1615/IHTC15.tdy.008636
pages 7763-7776


Ключевые слова: Statistical thermodynamics, molecular simulation, interfacial free energy, thermodynamic integration, phase transition, cleaving method

Аннотация

Sugar alcohols have been recently under investigation for their use as phase change materials in long-term heat storage systems. The thermal performances in such systems are strongly dominated by the nucleation and crystal growth kinetics, which on their turn are linked to the crystal-melt interfacial free energy γSL. We report a novel technique using first principle calculations to accurately predict γSL of xylitol and β-D-mannitol, as well as their anisotropy, from molecular modeling. The molecular model is based on a wellproven generalized AMBER force field, which can reliably reproduce the physics during the phase change. The calculation technique is generalized from a cleaving method which has been successfully implemented in monoatomic and rigid polyatomic molecular systems. This method essentially creates an artificial interface and gradually puts the crystal and melt phases into contact under the guidance of a cleaving potential. We extended this method for the calculation of flexible polyatomic molecules. A specific cleaving potential is designed for molecular systems with many degrees of freedoms. We made many efforts to achieve reliable equilibrium Boltzmann sampling and reduction of hysteresis, including the selection of transition paths. The samples of transition states are processed based on the Bennett Acceptance Ratio method. The predicted free energies agree with available experimental estimations, and the large anisotropy in the interfacial free energy is found which could be responsible for the dendritic growth of xylitol and D-mannitol systems as observed in experiments.

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