论文标题
SCF3中负热膨胀的从头算分子动力学模拟：超级细胞尺寸的效果
Ab initio molecular dynamics simulations of negative thermal expansion in ScF3: the effect of the supercell size
论文作者
论文摘要
氟化扫描（SCF3）属于一类负热膨胀（NTE）材料。它显示出强大的晶格收缩，可在较高温度下切换到约1000 K。在这里，使用等效分子动力学（AIMD）模拟在温度范围内研究了SCF3中的NTE效应。晶格常数，原子间SC-F-SC键角分布以及SC-F和SC-SC径向分布函数的温度依赖性是从2A x 2a x 2a到5A x 5a x 5a的超级细胞大小的函数，其中A是SCF3的晶状体参数。与600 K处的实验SC K-EXEFS数据进行比较以验证AIMD模拟的准确性。我们的结果表明，AIMD计算能够在SCF3中定性地重现NTE效应，但是，应使用大于2A x 2a x 2a的超大小来准确解释动态障碍。 SCF3中NTE的起源是通过SCF6 Octahedra的扩展与旋转之间的相互作用来解释的。
Scandium fluoride (ScF3) belongs to a class of negative thermal expansion (NTE) materials. It shows a strong lattice contraction up to about 1000 K switching to expansion at higher temperatures. Here the NTE effect in ScF3 is studied in the temperature range from 300 K to 1600 K using ab initio molecular dynamics (AIMD) simulations in the isothermal-isobaric (NpT) ensemble. The temperature dependence of the lattice constant, inter-atomic Sc-F-Sc bond angle distributions and the Sc-F and Sc-Sc radial distribution functions is obtained as a function of supercell size from 2a x 2a x 2a to 5a x 5a x 5a where a is the lattice parameter of ScF3. A comparison with the experimental Sc K-edge EXAFS data at 600 K is used to validate the accuracy of the AIMD simulations. Our results suggest that the AIMD calculations are able to reproduce qualitatively the NTE effect in ScF3, however a supercell size larger than 2a x 2a x 2a should be used to account accurately for dynamic disorder. The origin of the NTE in ScF3 is explained by the interplay between expansion and rotation of ScF6 octahedra.
