Optical, synchrotron X-ray and neutron diffraction investigations of structural changes in the layered compound K2Na[Ag(CN)2]3

We report a study of single-crystal Raman scattering, powder synchrotron X-ray and neutron diffraction as well as specific heat for the layered compound K2Na[Ag(CN)2]3 in the temperature range 2–300 K. Analysis of the Raman scattering data provides evidence for structural changes at approximately 210 K. Synchrotron X-ray and neutron powder diffraction results indicate essential, gradual changes with temperature in the range from 1.5 to 300 K and in particular small, but significant deviations from trigonal symmetry of the pseudo-hexagonal lattice parameters a=aortho/3,b below approximately 210 K. The c-lattice parameter increases anomalously with decreasing temperature.