B_4C晶体的结构与C原子占位研究

Structure and C atom occupied position of the B_4C crystal

设计了多种B4C结构模型,并对模型进行了结构优化,计算了各模型结构的单点能。结果表明,B4C的稳定结构为CBC(B11C),即它由C-B-C三原子链和B11C二十面体组成,B11C中C原子为极地占位。由于双极地占位的B10C2+B12结构能量与B11C结构相差较小,在通常材料制备条件下,B4C晶体中有少量B10C2+B12结构的存在是可能的。计算结果表明,B11C中极地C原子占位分布为有序化时能量较低,当B4C晶体在能量最低的平衡态时C原子在B11C二十面体中的占位应有一定的有序性。

This paper designed various B4C structure model, and carries on a structure optimization to the model, computed final energy of each structure model. As a result, the stable structure of B4C crystal is CBC（B11C）, namely be from the C-B-C three atom chains and B11C icosahedron constitutes, C atom occupy a polar position in B11C. Because the difference of bipolar occupied B10C2＋B12 structure energy and P11C unit is smaller, it is possible that there is little B10 C2 ＋ B12 structure exist in B4C crystal usually making condition. Computed result shown, in B11C the C atom occupied position as order distribution the energy be lower. When the B4C crystal at the energy lowest equilibrium state the C atom occupying position in the B11C icosahedron should have a certain order.