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Ionic interaction in a platinum chloride linear chain: PtCl

The authors have modified their previous model of MX chain materials to better describe the highly valence localized platinum chloride linear chain compounds, e.g., PtCl. The nearest neighbour Coulomb attraction and metal ion-ion electrostatic repulsion are added to the authors previous Hamiltonian. These two interactions play two roles: generating (i) an effective anharmonic intra-site electron-phonon coupling (therefore leading to the formation of charge-density-wave even if the inter-site electron-phonon coupling is weak) and (ii) acting as an effective elastic force between neighboring Pt and Cl atoms. Uniform and various defect states (polaron, bi-polaron and exciton) have been studied within this framework by computing their optical absorption, resonance Raman (RR) and infrared spectra. The results agree with the experimental data very well. Buckling of Cl atoms out of the chain is found to be important in order to obtain correct frequencies of RR modes of electron polarons and bi-polarons.

resonance Raman spectra ; ionic interaction ; MX chain materials ; anharmonic intra-site electron-phonon coupling ; polaron ; bipolaron

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