Jakse N, Pasturel A
Sciences et Ingénierie des Matériaux et Procédés, UMR CNRS 5266, Grenoble INP, BP 75, 38402 Saint-Martin d'Hères Cedex, France.
J Chem Phys. 2014 Dec 21;141(23):234504. doi: 10.1063/1.4903452.
In the present work, the structural and dynamic properties of liquid and undercooled boron are investigated by means of ab initio molecular dynamics simulation. Our results show that both liquid and undercooled states present a well pronounced short-range order (SRO) mainly due to the formation of inverted umbrella structural units. Moreover, we observe the development of a medium-range order (MRO) in the undercooling regime related to the increase of inverted umbrella structural units and of their interconnection as the temperature decreases. We also evidence that this MRO leads to a partial crystallization in the β-rhombohedral crystal below T = 1900 K. Finally, we discuss the role played by the SRO and MRO in the nearly Arrhenius evolution of the diffusion and the non-Arrhenius temperature dependence of the shear viscosity, in agreement with the experiment.
在本工作中，通过从头算分子动力学模拟研究了液态和过冷硼的结构与动力学性质。我们的结果表明，液态和过冷态均呈现出明显的短程有序（SRO），这主要归因于倒伞形结构单元的形成。此外，我们观察到在过冷区域中出现了中程有序（MRO），它与倒伞形结构单元数量的增加以及随着温度降低它们之间相互连接的增强有关。我们还证明，这种MRO在T = 1900 K以下导致了β - 菱面体晶体的部分结晶。最后，我们讨论了SRO和MRO在扩散的近似阿仑尼乌斯演化以及剪切粘度的非阿仑尼乌斯温度依赖性中所起的作用，这与实验结果一致。
