paper

First principles calculations of X-ray absorption in an ultrasoft pseudopotentials scheme: from $I^\pm$ -quartz to high-T $_{c}$ compounds

arXiv:0906.0897

Abstract

We develop a first-principles scheme based on the continued fraction approach an d ultrasoft pseudopotentials to calculate K-edge X-ray absorption spectra in solids. The method allows for calculations of K-edge X-ray absorption spectra in transition metal and rare-earths compounds with substantially reduced cutoffs respect to the norm-conserving case. We validate the method by calculating Si and O K-edges in $I^\pm$ quartz, Cu K-edge in Copper and in La $_{2}$ CuO $_{4}$ . For the case of Si and O edges in $I^\pm$ quartz and in Copper we obtain a good agreement with experimental data. In the Cu K-edge spectra of La $_{2}$ CuO $_{4}$ , a material considered a real challeng e for density functional theory we attribute all the near-edge and far-edge peaks to single particle excitations.

minor corrections, some references added, 9 pages, 5 figures, to appear on Phys. Rev. B

First principles calculations of X-ray absorption in an ultrasoft pseudopotentials scheme: from I^±-quartz to high-Tc​ compounds

Abstract

First principles calculations of X-ray absorption in an ultrasoft pseudopotentials scheme: from $I^\pm$ -quartz to high-T $_{c}$ compounds