Visible-spectroscopy study of the low dimensional (C2H5NH3)(2)CuCl4 compound in the region of its low temperature phase transitions

摘要

On the basis of absorption spectroscopy data the temperature evolution of Cu2+ ion environment in the layered compound (C2H5NH3)(2)CuCl4 was studied within the temperature range of 4.5-310 K. For the detailed analysis of the experimental data the specially created program package Crys Tool 1.0 based on the quantum mechanical models first of all on the model of normalised spherical harmonics (NSH) was used. It has been found that the crystal structure in the low temperature phases contains tetragonally distorted octahedral metal-halogen complexes. The parameters of crystal field, normalised spherical harmonics, angular overlap model as well as the metal-halogen distances show anomalous behaviour at the points of phase transitions: T-c = 10 K and T-4 = 232 K (for heating). The changes of these parameters observed around T-5 = 65 K also may be related to previously unknown phase transition. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.