Static and dynamic ionic structure of molten CaCl 2 via first-principles molecular dynamics simulations
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ORIGINAL PAPER
Static and dynamic ionic structure of molten CaCl2 via first-principles molecular dynamics simulations Min Bu 1,2 & Wenshuo Liang 1,2 & Guimin Lu 1,2 & Jianguo Yu 1,2 Received: 21 August 2020 / Revised: 16 November 2020 / Accepted: 18 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Molten CaCl2 could further broaden and open up new solar power applications due to its high melting point and chemical stability. However, few studies have focused on the ionic structure of molten CaCl2 with the experimental limitations such as extremely high temperature, high corrosiveness, and water absorbency, so that static and dynamic structure of molten CaCl2 has not been well understood. In this work, the static and dynamic ionic structure of molten salts was investigated by conducting firstprinciples molecular dynamics simulations. Structural features like short-range order and intermediate-range order are observed in molten CaCl2. The 6-coordinated structure stays dominant in the CaCl2 melt among the temperature range of 1100–1500 K. The network structure is filled with distorted octahedron which tends to be rutile structure, and these octahedrons are linked via corner-sharing and edge-sharing models. Among the temperature range of 1100–1500 K, the increase of temperature can accelerate the movement of ions, but there is no obvious effect on the local ionic structure of molten CaCl2. Analysis in this paper may be supportive to fill the gap in understanding the ion behavior of molten CaCl2 and other divalent chlorides. Keywords First-principles molecular dynamics . Molten CaCl2 . Ionic structure . Network structure
Introduction Molten salts have been intensively used in a wide range of fields including concentrating solar power system [1, 2], hightemperature fuel cell [3], and electrolysis process [4]. Recently, chloride molten salts have a bright application prospect as heat transfer fluid in high-temperature solar power generation because of their excellent thermal stability and heat storage performance [5, 6]. Being one of the most common chloride molten salts, molten CaCl2 that possesses a high melting point and stable chemical property could further broaden and open up new applications in many fields in the future. Limiting experimental conditions such as high temperature and high corrosiveness make the experimental studies difficult to perform. In the late 1980s and 1990s, a few conventional * Guimin Lu [email protected] 1
School of Resources and Environmental Engineering, East China University of Science and Technology, Shanghai 200237, China
2
Engineering Research Center of Resources Process Engineering, Ministry of Education, Shanghai, China
thermo-kinetic property experiments [7, 8] and spectroscopy studies were performed to explore the physical properties and local ionic structure of molten chloride in previous researches. Neutron scattering [9, 10] and X-ray scattering [11–13] have been often used to explore the local structure of molten chloride salts. Even so
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