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There has been considerable interest in properties of condensed matter at finite temperature, including non-equilibrium behavior and extreme conditions up to the warm dense matter regime. Such behavior is encountered, e.g., in experimental time resolved x-ray absorption spectroscopy (XAS) in the presence of intense laser fields. In an effort to simulate such behavior, we present an approach for calculations of finite-temperature x-ray absorption spectra in arbitrary materials, using a generalization of the real-space Greens function formalism. The method is incorporated as an option in the core-level x-ray spectroscopy code FEFF10. To illustrate the approach, we present calculations for several materials together with comparisons to experiment and with other methods.
We present an ab initio theory of core- and valence resonant inelastic x-ray scattering (RIXS) based on a real-space multiple scattering Greens function formalism and a quasi-boson model Hamiltonian. Simplifying assumptions are made which lead to an
We revise critically existing approaches to evaluation of thermodynamic potentials within the Greens function calculations at finite electronic temperatures. We focus on the entropy and show that usual technical problems related to the multivalued na
Greens function methods within many-body perturbation theory provide a general framework for treating electronic correlations in excited states. Here we investigate the cumulant form of the one-electron Greens function based on the coupled-cluster eq
Inelastic losses in core level x-ray spectra arise from many-body excitations, leading to broadening and damping as well as satellite peaks in x-ray photoemission (XPS) and x-ray absorption (XAS) spectra. Here we present a practical approach for calc
We present a finite-temperature extension of the retarded cumulant Greens function for calculations of exited-state and thermodynamic properties of electronic systems. The method incorporates a cumulant to leading order in the screened Coulomb intera