Variation of the Jahn–Teller distortion with pressure in perovskite layers A2CuCl4. Influence on the charge‐transfer band

Abstract

AbstractThis work investigates the variation of the first charge‐transfer (CT) transition with pressure in the A2CuCl4 layered perovskites, in terms of structural changes, in particular, the local structure of the (CuCl6)4– octahedra. We show that pressure partially reduces the Jahn–Teller distortion. The decrease of the axial Cu–Cl distance, R ax, is an order of magnitude bigger than the decrease of the equatorial distance, R eq, but the in‐plane Cu–Cu distance reduction is almost twice that the sum of R ax and R eq, thus indicating pressure‐induce tilts. This phenomenon avoids suppression of the JT effect, keeping the (CuCl6)4– axial distortion above 10 GPa. Both the partial reduction of the JT distortion and tiliting can account for the CT redshift induced by pressure. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)