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We present a Projector Augmented-Wave (PAW) method based on a wavelet basis set. We implemented our wavelet-PAW method as a PAW library in the ABINIT package [ http://www.abinit.org ] and into BigDFT [ http://www.bigdft.org ]. We test our implementation in prototypical systems to illustrate the potential usage of our code. By using the wavelet-PAW method, we can simulate charged and special boundary condition systems with frozen-core all-electron precision. Furthermore, our work paves the way to large-scale and potentially order- N simulations within a PAW method. [ABSTRACT FROM AUTHOR]

X-ray absorption and X-ray magnetic circular dichroism (XMCD) are very powerful tools for probing the orbital and spin moments of each atomic species orbital of magnetic materials. In this work, we present the implementation of a module for computing the X-ray absorption and XMCD spectra into the VASP code. We provide a derivation of the absorption cross-section in the electric dipole approximation. The matrix elements, which make up the X-ray absorption cross-section for a given polarization of light, are then computed using either the momentum operator p or the position operator r , within the projector augmented wave method. The core electrons are described using the relativistic basis-set whereas for the valence electrons, the spin–orbit coupling is added perturbatively to the semi-relativistic Hamiltonian. We show that both the p and the r implementations lead to the same results. The results for the K-edge and L 23 -edges of b c c -iron are then computed and compared to experiment. [ABSTRACT FROM AUTHOR]

Optical properties of warm dense matter are computed within linear response theory using the Kubo-Greenwood formula in the framework of Density Functional Theory and the Projector Augmented–Wave (PAW) method. For transition metals, the effect of spin-orbit coupling (SOC) has to be taken into account. We present the theoretical framework to introduce SOC in the PAW formalism and then to compute optical properties including SOC using the Kubo-Greenwood formula. This formulation has been implemented in the abinit software. Moreover, for high energy absorption spectra, we use Dirac relativistic core wave functions from the atompaw code to obtain the correct SOC energy splitting. This implementation enables a description of optical properties for warm dense metals including SOC for both core and valence orbitals. Example calculations are presented for warm dense gold and copper. [ABSTRACT FROM AUTHOR]