Low-temperature topotactic intercalation of a metallic dense host matrix chalcogenide: structural and electronic properties of Li_xMo₂SbS₂ (0 < x <0.7)

Alexandros Lappas Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, Greece.

Low-temperature reduction of existing hosts by solvated electrons is an attractive soft-chemistry strategy where control over the oxidation state of constituent atoms can lead to chemical compounds displaying novel physical properties. In this work we utilise Rietveld analysis of high-resolution neutron powder diffraction data (1.5 < T < 290 K) to demonstrate the capability of the ternary chalcogenide Mo₂SbS₂ to serve as a host system. Effort was placed in optimizing the properties of this dense host matrix material by successful intercalation of lithium in the one-dimensional channels of the structure. The incremental control of the geometrical, chemical and electronic environment in the Li_xMo₂SbS₂ series (0 < x < 0.7) is confirmed by synchrotron X-ray diffraction and temperature dependent transport measurements. Metallic electronic conductivity is found for all compositions ( 0 < x < 0.7) studied down to 2 K. The effect of the intercalation is uncovered by first-principles geometry optimizations and electronic structure calculations (DFT). The derivation of a large electron-phonon coupling constant for the parent compound (lambda _t = 2.4) supports its candidacy for superconducting behaviour. However, applied pressure (P < 17 kbar) does not drive the material through a metal-to-superconductor transition. The evolution of lambda_t upon lithiation postulates that the majority of the donated electrons become localised at the Mo-sites, giving rise to a polaron formation and relatively low carrier mobility.

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