Projector augmented wave calculation of x-ray absorption spectra at theL2,3edges

Abstract

We develop a technique based on density functional theory and the projector augmented wave method in order to obtain the x-ray absorption cross section at a general edge, both in the electric dipole and quadrupole approximations. The method is a generalization of Taillefumier et al., [Phys. Rev. B 66, 195107 (2002)]. We apply the method to the calculation of the Cu L 2,3 edges in fcc copper and cuprite (Cu 2 O), and to the S L 2,3 edges in molybdenite (2H-MoS 2 ). The role of core-hole effects, modeled in a supercell approach, as well as the decomposition of the spectrum into different angular momentum channels are studied in detail. In copper we find that the best agreement with experimental data is obtained when core-hole effects are neglected. On the contrary, core-hole effects need to be included both in Cu 2 O and 2H-MoS 2 . Finally we show that a non-negligible component of S L 2,3 edges in 2H-MoS 2 involves transition to states with s character at all energy scales. The inclusion of this angular momentum channel is mandatory to correctly describe the angular dependence of the measured spectra. We believe that transitions to s character states are quantitatively significant at the L 2,3 edges of third row elements from Al to Ar.

Vacuum ultraviolet excitation luminescence spectroscopy of few-layered MoS2

“…The s-or d-like DOS near to the sulfur atoms were revealed via soft x-ray absorption near-edge structures (XANES) [24,25]. However, no general information about the other band transitions from VB to CB could be given by the XANES due to the dominant dipole transition in the core-level excitations of the sulfur 2p electrons [25]. On another hand, to the best of our knowledge, studies of the excitation spectra of the lowdimensional MoS 2 are still lacking.…”

“…Though VB structures of the cleaved MoS 2 single-crystal flake were revealed by the angularresolved photoemission spectroscopy (ARPES) [23], the probe of the CB structure is beyond the reach of the ARPES technique. The CBs were also investigated through the x-ray absorption spectroscopy, but so far these studies were applied only to the bulk 2H-MoS 2 [24,25]. More band structures and transition mechanisms of the low-dimensional MoS 2 await to be revealed, however, with incident sources of tunable photon energies.…”

Thermodynamic and spectroscopic properties of oxygen on silver under an oxygen atmosphere

“…[74][75][76] Within this approach a single atom in the computational cell is treated as the absorbing atom, which, depending on the importance of the core hole effect, can be modeled with or without a core hole. 76,77 For the cases reported herein we report results using a full core hole unless otherwise noted, that is, results obtained by performing a SCF calculation on systems with a pseudopotential containing a core hole on the absorbing atom and the same k point mesh as was used in the SCF calculations. As in the case of the DSCF calculations, the excited core electron is included self consistently, unless otherwise noted (see Appendix D).…”

“…In a single particle approach the X-ray Absorption cross section for dipole transitions can be expressed using Fermi's Golden rule: [73][74][75][76] …”

X-ray magnetic and natural circular dichroism from first principles: Calculation of K - and L1 -edge spectra

“…48 The determination of all empty states in Eq. (17) would require a lot of computing resources and, as a consequence, would limit the size of the manageable supercell.…”