Physical properties of(NH4)2[Pt(CN)4]Cl0.42·3H2O: A new quasi-one-dimensional conductor

Abstract

The quasi-one-dimensional conductor ${(\mathrm{N}{\mathrm{H}}_{4})}_{2}$[${\mathrm{Pt}(\mathrm{CN})}_{4}$]${\mathrm{Cl}}_{0.42}$\ifmmode\cdot\else\textperiodcentered\fi{}3${\mathrm{H}}_{2}$O, ACP(Cl), has been studied experimentally by means of electrical conduction measurements, x-ray diffuse scattering, and neutron inelastic scattering. This allows the determination of all the physical parameters of interest for the theoretical description of the way, in which the Peierls instability manifests itself. ACP(Cl) appears as an analog of the well-studied isostructural compound ${\mathrm{K}}_{2}$[${\mathrm{Pt}(\mathrm{CN})}_{4}$]${\mathrm{Br}}_{0.3}$\ifmmode\cdot\else\textperiodcentered\fi{}3${\mathrm{H}}_{2}$O, KCP(Br), with three major changes. First, an increased intrachain Pt-distance in ACP(Cl) causes the metallic conductivity ${\ensuremath{\sigma}}_{m}$ to drop, and second, an increased Fermi wave vector ${k}_{F}$ introduces a change in the electron-phonon coupling constant $\ensuremath{\lambda}$ via the bare phonon frequency $\ensuremath{\omega}(2{k}_{F})$. Third, the interchain coupling $\ensuremath{\eta}$ is enhanced in ACP(Cl), which seems to be related to the hydrogen bonding of the N${\mathrm{H}}_{4}^{+}$ ions. We also present and discuss the frequency dependence of the conductivity at frequencies up to 1 MHz.