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Issue 46, 2018
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The dp type π-bond and chiral charge density waves in 1T-TiSe2

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Based on the atomic electronic configuration and Ti–Se coordination, a valence bond model for the layered transition metal dichalcogenide (TMDC) 1T-TiSe2 is proposed. 1T-TiSe2 is viewed as being composed of edge-sharing TiSe4-plaquettes as TiSe2-ribbon chains in each layer via a directional valence shell electron distribution as chemical bonds, in contrast to the conventional layer view of face-sharing TiSe6-octahedra. The four valence electrons per Ti in the hybridized dsp2-orbitals of square coordination form σ-bonds with the four nearest neighbor Se atoms in the chain. The electrons in the lone pair of the Se-4pz orbital are proposed to form a dp type π-bond via side-to-side orbital overlap with the empty Ti-3dxz/3dyz orbitals within each chain, which is positively supported by quantum chemistry calculations. A study of electron energy loss spectroscopy (EELS) with transmission electron microscopy (TEM) for 1T-TiSe2 is presented to show an energy loss near ∼7 and ∼20 eV, which confirms the existence of collective plasmon oscillations with the predicted effective electron numbers for the π- and (π + σ)-bond electrons, respectively.

Graphical abstract: The dp type π-bond and chiral charge density waves in 1T-TiSe2

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The article was received on 11 Sep 2018, accepted on 20 Oct 2018 and first published on 22 Oct 2018

Article type: Paper
DOI: 10.1039/C8DT03663B
Dalton Trans., 2018,47, 16509-16515

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    The dp type π-bond and chiral charge density waves in 1T-TiSe2

    G. Shu, S. Liou, C. Lin, M. Hayashi and F. Chou, Dalton Trans., 2018, 47, 16509
    DOI: 10.1039/C8DT03663B

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