Department of Chemistry and Green-Nano Materials Research Center , Kyungpook National University , 80 Daehak-ro , Buk-gu, Daegu , 41566 , South Korea.
Department of Physics , Novosibirsk State University , Pirogova str. 2 , Novosibirsk 630090 , Russia.
Nano Lett. 2019 Mar 13;19(3):1570-1576. doi: 10.1021/acs.nanolett.8b04421. Epub 2019 Feb 14.
For the first time, lonsdaleite-rich impact diamonds from one of the largest Popigai impact crater (Northern Siberia) with a high concentration of structural defects are investigated under hydrostatic compression up to 25 GPa. It is found that, depending on the nature of a sample, the bulk modulus for lonsdaleite experimentally obtained by X-ray diffraction in diamond-anvil cells is systematically lower and equal to 93.3-100.5% of the average values of the bulk moduli of a diamond matrix. Density functional theory calculations reveal possible coexistence of a number of diamond/lonsdaleite and twin diamond biphases. Among the different mutual configurations, separate inclusions of one lonsdaleite (001) plane per four diamond (111) demonstrate the lowest energy per carbon atom, suggesting a favorable formation of single-layer lonsdaleite (001) fragments inserted in the diamond matrix. Calculated formation energies and experimental diamond (311) and lonsdaleite (331) powder X-ray diffraction patterns indicate that all biphases could be formed under high-temperature, high-pressure conditions. Following the equation of states, the bulk modulus of the diamond (111)/lonsdaleite (001) biphase is the largest one among all bulk moduli, including pristine diamond and lonsdaleite.
首次对来自最大的波波加伊撞击坑（北西伯利亚）之一的富含六方氮化硼的撞击钻石进行了静水压缩研究，其浓度很高，结构缺陷也很高，达到了 25 GPa。研究发现，根据样品的性质，在金刚石对顶砧中通过 X 射线衍射实验获得的六方氮化硼的体弹性模量系统地低于和等于金刚石基质体弹性模量平均值的 93.3-100.5%。密度泛函理论计算揭示了可能存在多种金刚石/六方氮化硼和孪晶金刚石双相的共存。在不同的相互配置中，每个金刚石（111）中包含一个六方氮化硼（001）平面的单独夹杂物显示出每个碳原子的最低能量，表明插入金刚石基质中的单层六方氮化硼（001）碎片的有利形成。计算的形成能和实验金刚石（311）和六方氮化硼（331）粉末 X 射线衍射图谱表明，所有双相都可以在高温高压条件下形成。根据状态方程，金刚石（111）/六方氮化硼（001）双相的体弹性模量是所有体弹性模量中最大的，包括原始金刚石和六方氮化硼。
