Theoretical simulations and interpretations of x-ray-absorption near-edge data at the Ti and O K edges in titanium oxides, rutile, and anatase, have been performed in the framework of full multiple scattering theory and a tight-binding linear muffin-tin orbital band-structure method. Good agreement between experimental data and theoretical calculations is obtained, especially in the preedge region of the Ti K-edge spectrum which is interpreted in terms of mixing between the central Ti 4 p and neighboring Ti 3d orbitals in octahedral coordination. It is concluded that the positions of these latter Ti atoms relative to the photoabsorber influence in a noticeable way the intensity, width, and position of the features in the preedge region, which mainly originate from dipole transitions. Previous work on the subject is reexamined in the light of the present findings.

Sulfur K-edge x-ray-absorption spectra have been recorded for lithium intercalated titanium disulfides Li x TiS 2 . The near-edge features up to 30 eV above threshold are interpreted in the framework of full multiple-scattering theory. We show that the electrons transferred from intercalated lithium atoms are not only located on Ti 3d orbitals, as previously assumed, but also on the S 3p states. For comparison, we present the S p-projected density of states derived from linear muffin-tin-orbital band structure calculations. An overall agreement between measurement and theory is very well achieved.[S0031-9007(96)00962-3] PACS numbers: 78.70.Dm, 71.20.Lp, 72.80.Ga Lamellar transition metal dichalcogenides (TMDC) MX 2 (X S, Se; M Ti, Zr, Hf, V, Nb, Ta, Mo, or W) have been among the first phases considered as a host in intercalation reaction in which a guest species, atom, ion, or molecule can be reversibly inserted into empty spaces of the host structure [1][2][3][4]. Until quite recently, it has been thought that the guest species provides an electron to the transition metal (TM) d orbitals [5][6][7][8]. Such a conclusion is mainly based on a rigid band model. More recent investigations [9,10] tend to show that this model is not adequate to study the intercalation process. Moreover electronic band structure calculations [11] in the extended Hückel approach have shown that, in the case of lithium intercalation into titanium disulfide TiS 2 , there exists a partial electronic transfer of lithium 2s electron to the host structure, on both titanium and sulfur atoms. However, such an approach remains qualitative and is not able to explain the edge shape changes, especially in separating structural and electronic effects. To do so, it is necessary to combine accurate electronic band structure calculations and edge simulations. In this Letter, we present new x-ray absorption spectroscopy (XAS) data and theoretical analyses on the Li intercalated compound TiS 2 that demonstrate the important role of sulfur atoms and provide a correct picture in the intercalation process on TMDC.TiS 2 has been prepared as described in Ref. [12]. Lithium intercalation has been performed by the n-butyl lithium technique at room temperature [13] with the lithium content determined by flame spectroscopy. In order to prevent degradation, samples were handled in glove boxes and transferred to the different systems for analysis via appropriate airtight containers. X-ray appearance near-edge structure (XANES) spectra were recorded using the French synchrotron radiation source at LURE (Orsay). The sulfur K edge was recorded on the Super ACO storage ring with a Si111 two-crystal monochromator, with a 0.4 eV resolution.All the computations of the XANES spectra were carried out using the multiple-scattering CONTINUUM code [14] based on the one-electron full multiple-scattering (MS) theory [15][16][17]. The cluster potential was approximated by a set of spherically averaged muffin-tin (MT) potential, which was built by following the standard Mattheis...

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