Bond switching from two- to three-dimensional polymers of C60 at high pressure

Abstract

In situ high pressure x-ray diffraction experiments revealed that a transformation from the twodimensional (2D) tetragonal C60 polymer to a three-dimensional (3D) polymer takes place via a highly anisotropic deformation of C60 molecules along the c axis, as an irreversible first-order transformation above 20 GPa. In the 3D polymer phase, the 2+2 bonds remain in the 2D plane, while neighboring layers are connected by the 3+3 bonds. The bulk modulus of the 3D polymer was 407 GPa, being slightly smaller than that of diamond.