The role of carbon in the formation of alpha boron at high pressure and high temperature (HPHT) has been investigated by combining HPHT experiments and density functional theory (DFT) calculations. Starting from beta rhombohedral or amorphous boron and amorphous carbon at 5 GPa, the alpha boron phase has been repeatedly observed between 1473 K and 2273 K, at temperatures that are much higher than those reported in the phase diagram of boron. The DFT investigation of the effect of carbon insertion into the alpha rhombohedral boron atomic structure on the formation enthalpy, volume and optical properties shows that only the (B11C) substituted icosahedron defect accounts for the slight volume contraction observed in α boron. It is also compatible with the observed red colour of α boron crystals, and consistently has a very low formation energy. Our calculations also provide a calibration tool to evaluate the carbon concentration in the samples. Finally, the synthesis temperature is found to be an easy means to tune the carbon concentration on demand.
Deep-UV bleaching of charge disorder in encapsulated graphene
University of Manchester（曼彻斯特大学）；National Graphene Institute, University of Manchester（国家石墨烯研究所，曼彻斯特大学）；National Institute for Materials Science（国立材料科学研究所）；University of Lancaster（兰卡斯特大学）
Surface defects in carbon-doped hexagonal boron nitride for negative-contrast direct laser writing
National University of Singapore（新加坡国立大学）；Institute for Functional Intelligent Materials, National University of Singapore（新加坡国立大学功能智能材料研究所）；National Institute of Material Science（日本物质材料研究机构）；Research Center for Functional Materials, National Institute of Material Science（日本物质材料研究机构功能材料研究中心）；International Center for Materials Nanoarchitectonics, National Institute of Material Science（日本物质材料研究机构国际纳米材料中心）
