Molecular arrangement and electronic band structure of θ-(BEDT-TTF) ₂CsZn(SCN)₄ controlled by uniaxial compression

Using the uniaxial strain method, the lattice parameters and the atomic positions of the quasi-two-dimensional organic conductor θ-(BEDT-TTF)₂CsZn(SCN)₄ were measured at room temperature with piston pressures up to 10 kbar applied parallel to the c-axis in the conducting plane. The lattice parameter c was predominantly reduced with increasing the piston pressure although a small Poisson's effect occurred in the parameter a. Band calculation showed that the transfer integrals under the uniaxial compression by the piston pressure of 10 kbar became similar to those of θ-(BEDT-TTF)₂ RbZn(SCN)₄. This result is consistent with that of transport measurements reported already and suggests that a charge disproportionation, which has been observed in the RbZn-compound, occurs also in the present compound under the uniaxial compressive strain.