A xanes study of the CuK-edge in A(2)CuCl(4) perovskite layers under pressure. Influence of antiferrodistortive structure

This work investigates the X-ray absorption spectra of the Cu K-edge in the layered compounds (CnH2n+1NH3)(2)CuCl4 (n=1-3) and their variation with pr essure. The XANES spectra show a three peaked structure around 8.98 KeV at zero pressure which is characteristic of Cu2+ complexes in D-4h symmetry. A pplication of hydrostatic pressure induces a progressive reduction of the e nergy separation between the second and third peaks that has been interpret ed in terms of a progressive disappearance of the antiferrodistortive struc ture exhibited by the Cu2+ complexes in this compound series. The results a re compared with recent pressure experiments on Raman and Charge Transfer s pectroscopy as well as with Multiple Scattering calculations performed on t hese layered systems.