Simplified force field for molecular dynamics simulations of amorphous SiO2 for solar applications
Simplified force field for molecular dynamics simulations of amorphous SiO2 for solar applications
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DOI：
10.1016/j.ijthermalsci.2020.106647
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发表时间：
2021-02-01
影响因子：
4.5
通讯作者：
Ding, Yulong
中科院分区：
文献类型：
--
作者：
Anagnostopoulos, Argyrios;Alexiadis, Alessio;Ding, Yulong
熔融盐（例如NaNO 3、KNO 3）与α-SiO2纳米颗粒的混合物在集中式太阳能发电中具有作为热能储存材料和传热流体的潜在应用。在这项研究中，提出了一套Lennard-Jones参数的无定形二氧化硅，旨在了解熔盐/无定形二氧化硅界面在纳米尺度上通过分子动力学模拟。目前用于模拟α-SiO2的力场没有经过验证的交叉项相互作用规则，或者计算成本很高。在这项工作中，一组新的Lennard-Jones参数能够准确地模拟非晶SiO2的结构。它的优点是它具有精确的验证混合规则，可用于模拟交叉项（不同物种）相互作用，这在涉及界面的模拟中占主导地位。实验结果和先前研究的数据验证了所提出的势：所有计算的性质（即径向分布、角分布、平均键长、配位数、密度、热膨胀系数和热导率）与文献中的数据一致。此外，熔融盐-无定形二氧化硅界面进行了研究。观察到在液体-纳米颗粒界面处存在压缩液体层。熔盐混合物的密度被发现是显着较高的自扩散率较低，在界面附近。最后，Na+和K+离子似乎是有序的界面附近，表明存在一个有序的双层。
Mixtures of molten-salts (e.g. NaNO3, KNO3) with alpha-SiO2 nanoparticles have potential applications in concentrated solar power generation both as a thermal energy storage material and heat transfer fluid. In this study, a set of Lennard-Jones parameters for amorphous silica is proposed, aimed at understanding the molten-salt/ amorphous-silica interface at the nanoscale through molecular dynamics simulations. Current force fields used for the simulation of alpha-SiO2 do not have validated rules for cross-term interactions or are computationally expensive. In this work, a novel set of Lennard-Jones parameters capable of accurately simulating the structure of amorphous SiO2 is presented. Its advantage is that it has precise validated mixing rules, which can be used to model cross term (different species) interactions, which are dominant in simulations involving interfaces. The proposed potential is validated by experimental results and data from previous studies: all the calculated properties (i.e. radial distribution, angular distribution, mean bond length, coordination number, density, thermal expansion coefficient and thermal conductivity) are in good agreement with the data in the literature. Additionally, the molten salt-amorphous silica interface is investigated. The existence of a compressed liquid layer at the liquid-nanoparticle interface is observed. The density of the molten salt mixture is found to be significantly higher and the self-diffusivity lower, in the proximity of the interface. Finally, the Na+ and K+ ions appear to be ordered in the proximity of the interface, indicating the existence of an ordered double-layer.