Unoccupied electron states ofTiS2studied by means of polarized x-ray absorption

Abstract

Using polarized x-ray-absorption spectroscopy along with band-structure and real-space multiple-scattering calculations, we have studied unoccupied states of TiS 2 . With respect to titanium and sulfur sites, the local angular momentum projections of the density of states are presented for states up to 25 eV above the Fermi level. Good agreement between experiment and theory suggests that quadrupole (1s→d) transitions in Ti K absorption are negligible compared to dipole (1s→p) transitions. We have applied a new technique for construction of pseudopotentials adapted to the chemical bond and found that previous calculation of electronic states with energies higher than 10 eV above Fermi level was not correct.

Polarized x-ray-absorption spectra ofTiS2,TiSe2,<

“…Exploratory XANES calculations for a whole series of smaller cluster sizes were performed to verify that a convergence with respect to the number of included atoms had been achieved. 7 The largest angular momentum included in the single-site scattering was L max ϭ4. Test calculations for all four edges with L max as large as 6 were done for clusters of 25 atoms with hardly any difference visible.…”

“…For the understanding of this weak bonding mechanism an analysis of the lowest unoccupied electron states can be helpful. Much effort was devoted to x-ray-absorption spectroscopy studies [4][5][6][7] of TiS 2 or of Li x TiS 2 intercalates. 8 However, to our knowledge no published study included a comparison of results for different titanium dichalcogenides, which definitely must correlate with each other and thus prove or negate the adopted conclusions.…”

Linear dichroism in 3d transition metal NEXAFS of correlated materials

“…• the localization of the Cu 3d hole preferred in the 3 the strong bulk sensitivity of the transmission mode which can be applied to K absorption as opposed to the surface sensitive yield modes which are usually used when measuring L absorption spectra. The quality of band structure and real-space multiple-scattering (RS-MS) calculations for reproducing experimental 3d metal K-NEXAFS and the consideration of core-hole effects has been investigated and proved by comparison with the appropriate spectra of TiS 2 , TiSe 2 , TiTe 2 and V 2 O 5 (Simunek et al, 1997;Bocharov et al, 1998;Sipr et al, 1999). A comparison of the experimental results with theoretical RS MS calculations show the sufficiency of one-electron model for the description of p-like states.…”

Spatial distribution of photoelectrons participating in formation of x-ray absorption spectra

“…The polarized Ti K edge XANES of TiS 2 shows a distinct pre-peak at the xy polarization (i.e., when the polarization vector of the incoming radiation lies within the titanium layer). 27,28 Relying on XANES calculations for artificial trial structures, Wu et al 27 suggested that the pre-edge is generated by multiple scattering which involves mainly the central Ti atom and the Ti atoms of the second coordination shell. A comprehensive analysis of the Ti K edge XANES of TiS 2 , including comparison between theory and experiment, can be found elsewhere.…”

“…A comprehensive analysis of the Ti K edge XANES of TiS 2 , including comparison between theory and experiment, can be found elsewhere. 27,28,24 Therefore, we present in Fig. 1 only the theoretical polarized pre-peak structure, calculated for a cluster of 135 atoms, together with P (j) , ∆P DOS curves for the central atom and for atoms of its four nearest coordination shells.…”