First-principles-based phase diagram of the cubic BNC ternary system
First-principles-based phase diagram of the cubic BNC ternary system
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DOI：
10.1103/physrevb.77.094121
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发表时间：
2008-03
影响因子：
3.7
通讯作者：
Koretaka Yuge;Atsuto Seko;Y. Koyama;F. Oba;I. Tanaka
中科院分区：
文献类型：
--
作者：
Koretaka Yuge;Atsuto Seko;Y. Koyama;F. Oba;I. Tanaka
用蒙特卡罗模拟和基于第一性原理计算的团簇展开技术研究了异质金刚石结构中立方BNC三元系的相图。所有的原子排列都表现出正的形成能，表明相分离为立方BN$(c\text{\ensuremath{-}}\mathrm{B}\mathrm{N})$和金刚石。这些排列显示出对B-N和C-C键的强烈偏好，而不利于B-C、C-N、B-B和N-N键沿第一近邻配位。这自然可以归因于各自第一近邻键的电子数过饱和和欠饱和。基于第一性原理的晶格动力学计算表明，金刚石与金刚石形成固溶体，降低了振动自由能，显著提高了金刚石相和富金刚石相的溶解度。在$T=4500\phantom{\rule{0.3em}{0ex}}\mathrm{K}$，上实现了完全混溶，其熔点高于钻石的熔点和熔点。
The phase diagram for the cubic BNC ternary system in a heterodiamond structure was examined by Monte Carlo simulations and the cluster expansion technique based on first-principles calculations. All the atomic arrangements exhibit positive formation energies, indicating phase separation into cubic BN $(c\text{\ensuremath{-}}\mathrm{B}\mathrm{N})$ and diamond. These arrangements show a strong preference for B-N and C-C bonds and disfavor B-C, C-N, B-B, and N-N bonds along the first nearest neighbor coordination. This can be naturally attributed to the oversaturation and undersaturation of the number of electrons for respective first nearest neighbor bonds. First-principles-based lattice-dynamics calculations reveal that the formation of a solid solution between $c\text{\ensuremath{-}}\mathrm{B}\mathrm{N}$ and diamond decreases vibrational free energy, resulting in a significant enhancement of the solubility for both $c\text{\ensuremath{-}}\mathrm{B}\mathrm{N}$ and diamond-rich phases. Complete miscibility is achieved over $T=4500\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, which is higher than the melting points of both diamond and $c\text{\ensuremath{-}}\mathrm{B}\mathrm{N}$.