摘要
The atomistic mechanism for direct conversion of graphite to diamond is a long-standing problem in condensed matter physics. The newly identified cold-compressed graphite phases of M, W and 0 carbon provide a crucial link to understand the graphite-to- diamond phase transformation. We demonstrate by ab initio calculations that pressure has a dual role in lowering the conversion barrier and enhancing the production stability during the first-stage cold-compressed phase conversion of graphite toward the intermediate metastable M, W and 0 carbon phases. However, it has little effect on the relative enthalpy and high conversion barrier during the second-stage conversion process toward the diamond polytypes, showing a temperature dominated conversion process. These results may give explanation regarding the necessity of high pressure and high temperature during the graphite-to- diamond reaction.
The atomistic mechanism for direct conversion of graphite to diamond is a long-standing problem in condensed matter physics.The newly identified cold-compressed graphite phases of M,W and O carbon provide a crucial link to understand the graphite-todiamond phase transformation.We demonstrate by ab initio calculations that pressure has a dual role in lowering the conversion barrier and enhancing the production stability during the first-stage cold-compressed phase conversion of graphite toward the intermediate metastable M,W and O carbon phases.However,it has little efect on the relative enthalpy and high conversion barrier during the second-stage conversion process toward the diamond polytypes,showing a temperature dominated conversion process.These results may give explanation regarding the necessity of high pressure and high temperature during the graphite-todiamond reaction.
基金
supported by the National Natural Science Foundation of China(Grant No.11274356)
the Ministry of Environmental Protection of China(Grant Nos.200909086 and 201109037)
