Shimizu Masahiro, Fukuyo Tsubasa, Matsuoka Jun, Nakashima Kento, Sato Kenzo, Kiyosawa Tomohiro, Nishi Masayuki, Shimotsuma Yasuhiko, Miura Kiyotaka
Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
School of Engineering, The University of Shiga Prefecture, Hikone 522-8533, Japan.
J Chem Phys. 2021 Feb 21;154(7):074501. doi: 10.1063/5.0040513.
The Soret effect in silicate melts has attracted attention in earth and material sciences, particularly in glass science and engineering, because a compositional change caused by the Soret effect modifies the material properties of silicate melts. We investigated the Soret effect in an NaO-SiO system, which is the most common representative of silicate melts. Our theoretical approach based on the modified Kempers model and non-equilibrium molecular dynamics simulation was validated for 30NaO-70SiO(mol. %). The sign and order of the absolute values of the calculated Soret coefficients were consistent with the experimental values. The positive Soret coefficient of SiO in the SiO-poor composition range was accurately predicted. Previous experimental studies have focused on SiO-rich compositions, and only the negative sign, indicating SiO migration to the hot side, has been observed. In the SiO-poor composition range, the Q structure was dominant and had four Si-O-Na bonds around an SiO unit. The Si-O-Na bond had high enthalpic stability and contributed to the large negative enthalpy of SiO mixing. According to our model, components with a large negative partial molar enthalpy of mixing will concentrate in the cold region. The microscopic and thermodynamic origins of the sign change in the Soret effect were determined.
硅酸盐熔体中的索雷特效应在地球科学和材料科学领域，尤其是玻璃科学与工程领域引起了关注，因为索雷特效应导致的成分变化会改变硅酸盐熔体的材料性能。我们研究了NaO-SiO体系中的索雷特效应，该体系是硅酸盐熔体最常见的代表。我们基于改进的肯佩斯模型和非平衡分子动力学模拟的理论方法在30NaO-70SiO（摩尔%）体系中得到了验证。计算得到的索雷特系数绝对值的符号和顺序与实验值一致。在贫SiO成分范围内SiO的正索雷特系数得到了准确预测。以往的实验研究集中在富SiO成分上，仅观察到了表明SiO向热端迁移的负号。在贫SiO成分范围内，Q结构占主导，在一个SiO单元周围有四个Si-O-Na键。Si-O-Na键具有较高的焓稳定性，并导致了SiO混合的大负焓。根据我们的模型，具有大负混合偏摩尔焓的组分将集中在冷区。确定了索雷特效应中符号变化的微观和热力学起源。
