Baker Paul A, Chen Wei-Chih, Chen Cheng-Chien, Catledge Shane A, Vohra Yogesh K
Department of Physics, University of Alabama at Birmingham, Birmingham, Alabama, 35294, USA.
Sci Rep. 2020 Mar 10;10(1):4454. doi: 10.1038/s41598-020-61462-9.
Density functional theory predictions have been combined with the microwave-plasma chemical vapor deposition technique to explore metastable synthesis of boron-rich boron-carbide materials. A thin film synthesis of high-hardness (up to 37 GPa) BC via chemical vapor deposition was achieved. Characterization of the experimental crystal structure matches well with a new theoretical model structure, with carbon atoms inserted into the boron icosahedra and 2b sites in a α-tetragonal B base structure. Previously reported metallic BC structures with carbons inserted only into the 2b or 4c sites are found to be dynamically unstable. The newly predicted structure is insulating and dynamically stable, with a computed hardness value and electrical properties in excellent agreement with the experiment. The present study thus validates the density functional theory calculations of stable crystal structures in boron-rich boron-carbide system and provides a pathway for large-area synthesis of novel materials by the chemical vapor deposition method.
密度泛函理论预测已与微波等离子体化学气相沉积技术相结合，以探索富硼碳化硼材料的亚稳合成。通过化学气相沉积实现了高硬度（高达37 GPa）BC薄膜的合成。实验晶体结构的表征与一种新的理论模型结构非常匹配，其中碳原子插入硼二十面体和α-四方B基结构的2b位点。先前报道的仅将碳插入2b或4c位点的金属BC结构被发现是动态不稳定的。新预测的结构是绝缘且动态稳定的，计算得到的硬度值和电学性质与实验结果高度吻合。本研究因此验证了富硼碳化硼体系中稳定晶体结构的密度泛函理论计算，并为通过化学气相沉积法大面积合成新型材料提供了一条途径。
