title: Amorphous diamond: a high-pressure superhard carbon allotrope.
abstract: Compressing glassy carbon above 40 GPa, we have observed a new carbon allotrope with a fully sp(3)-bonded amorphous structure and diamondlike strength. Synchrotron x-ray Raman spectroscopy revealed a continuous pressure-induced sp(2)-to-sp(3) bonding change, while x-ray diffraction confirmed the perseverance of noncrystallinity. The transition was reversible upon releasing pressure. Used as an indenter, the glassy carbon ball demonstrated exceptional strength by reaching 130 GPa with a confining pressure of 60 GPa. Such an extremely large stress difference of >70 GPa has never been observed in any material besides diamond, indicating the high hardness of this high-pressure carbon allotrope.
authors: Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA. lyforest@stanford.edu
authors: Yu
authors: Y
authors: Lin
authors: Li
authors: L
authors: Zhang
authors: Ho-kwang
authors: HK
authors: Mao
authors: Paul
authors: P
authors: Chow
authors: Yuming
authors: Y
authors: Xiao
authors: Maria
authors: M
authors: Baldini
authors: Jinfu
authors: J
authors: Shu
authors: Wendy L
authors: WL
authors: Mao