X-ray diffraction study of α-(BEDT-TTF)2I3 single crystal under high pressure Original Research Article

α-(BEDT-TTF)2I3 (α-ET2I3) is one of the well-known organic conductors, which undergoes a metal–insulator transition around 135 K at 1 atm. This metal–insulator transition can be suppressed by applying pressure. Recently, the transport property of α-ET2I3 under high pressure attracts many interests because of its peculiar behaviors. In order to investigate the origin of the peculiar transport property from the structural point of view, we performed X-ray structure analyses of α-ET2I3 single crystal under several pressures using diamond anvil cell at room temperature. The crystal structure was refined by usual least-square method. The rigid body approximation of ET molecules was not adopted. The lattice parameters and the I–I bond lengths of the I3− anions decrease with increasing pressure.