Real-space Green's function calculations of Compton profiles

Mattern, B.; Seidler, Gerald T.; Kas, J. J.; Pacold, J.I.; Rehr, J. J.

doi:10.1103/physrevb.85.115135

Cited by 23 publications

(25 citation statements)

References 84 publications

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“…First, many materials properties such as optical and x-ray spectra depend on quasi-particle or excited-state effects. For example, band-gaps depend on quasi-particle energies, and calculations of x-ray spectra [18] and Compton scattering require correlation corrections [19]. Although methods like quantum Monte-Carlo and the random phase approximation (RPA) can provide accurate correlation energies, they are not directly applicable to such excited state properties.…”

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confidence: 99%

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Finite Temperature Green’s Function Approach for Excited State and Thermodynamic Properties of Cool to Warm Dense Matter

Kas

Rehr

2017

Phys. Rev. Lett.

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We present a finite-temperature extension of the retarded cumulant Green's function for calculations of exited-state and thermodynamic properties of electronic systems. The method incorporates a cumulant to leading order in the screened Coulomb interaction W and improves excited state properties compared to the GW approximation of many-body perturbation theory. Results for the homogeneous electron gas are presented for a wide range of densities and temperatures, from cool to warm dense matter regime, which reveal several hitherto unexpected properties. For example, correlation effects remain strong at high T while the exchange-correlation energy becomes small. In addition, the spectral function broadens and damping increases with temperature, blurring the usual quasi-particle picture. Similarly Compton scattering exhibits substantial many-body corrections that persist at normal densities and intermediate T . Results for exchange-correlation energies and potentials are in good agreement with existing theories and finite-temperature DFT functionals. Finite temperature (FT) effects in electronic systems are both of fundamental interest and practical importance. These effects vary markedly depending on whether the temperature T is larger or smaller than the Fermi temperature T F (typically a few eV). At "cool" temperatures, where T is much smaller than T F , electrons are nearly degenerate, and Fermi factors and excitations such as phonons dominate the thermal behavior [1][2][3]. In contrast thermal occupations become nearly semi-classical and electronic excitations such as plasmons become important in the warm-dense-matter (WDM) regime, where T is of order T F or larger, and condensed matter is partially ionized. Recently there has been considerable interest in both experimental and theoretical investigations of WDM for applications ranging from laser-shocked systems and inertial confinement fusion to astrophysics [4,5]. Many of these studies focus on equilibrium thermodynamic properties, e.g., using the FT generalization of density functional theory (DFT) [6][7][8]. Although in principle, FT DFT is exact [9][10][11], practical applications require exchange-correlation functionals which must be approximated, e.g., by constrained fits [12] to theoretical electron gas calculations [8,[13][14][15][16][17]. However, these approaches have various limitations. First, many materials properties such as optical and x-ray spectra depend on quasi-particle or excited-state effects. For example, band-gaps depend on quasi-particle energies, and calculations of x-ray spectra [18] and Compton scattering require correlation corrections [19]. Although methods like quantum Monte-Carlo and the random phase approximation (RPA) can provide accurate correlation energies, they are not directly applicable to such excited state properties. Secondly, currently available exchangecorrelation functionals can exhibit unphysical behavior outside the range of validity of theoretical data [20]. On the other hand Green's function (GF) methods within...

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“…Occupation numbers can be measured e.g., by Compton scattering [19,50,51], and are sensitive to the many-body correlation effects in A k . Note that at low-T , A k (ω) exhibits multiple-satellites for k < k F while for k > k F and at T > T F , the quasiparticle peak broadens, and overlaps the satellites.…”

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Finite Temperature Green’s Function Approach for Excited State and Thermodynamic Properties of Cool to Warm Dense Matter

Kas

Rehr

2017

Phys. Rev. Lett.

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“…58 This formalism, which can treat complex, aperiodic systems, has been extensively applied to condensed-matter systems, where XRTS/NIXS provides a bulk-sensitive alternative to, and extension of, soft x-ray absorption spectroscopy, 49,[58][59][60][61][62][63] The RSGF approach has recently been extended to treat the valence contribution. 64 Starting with a description of atomic species and locations, an effective one-particle Green's function for the valence electrons in the cluster of atoms is calculated in the muffin-tin approximation, including the effects of full multiple scattering 55 . This Green's function implicitly contains the excited electronic states that are the final states in the scattering experiment.…”

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confidence: 99%

Theoretical treatments of the bound-free contribution and experimental best practice in X-ray Thomson scattering from warm dense matter

Mattern

Seidler

2013

Physics of Plasmas

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By comparison with high-resolution synchrotron x-ray experimental results, we assess several theoretical treatments for the bound-free (core-electron) contribution to x-ray Thomson scattering (i.e., also known as nonresonant inelastic x-ray scattering). We identify an often overlooked source of systematic error in the planewave form factor approximation (PWFFA) used in the inference of temperature, ionization state, and free electron density in some laser-driven compression studies of warm dense matter. This error is due to a direct violation of energy conservation in the PWFFA. We propose an improved practice for the bound-free term that will be particularly relevant for XRTS experiments performed with somewhat improved energy resolution at the National Ignition Facility or the Linac Coherent Light Source. Our results raise important questions about the accuracy of state variable determination in XRTS studies, given that the limited information content in low-resolution XRTS spectra does not strongly constrain the models of electronic structure being used to fit the spectra.

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“…Second, it is also a critical input parameter to any fine treatment of electronic structure. The electronic structure of dense crystalline systems and plasmas, in turn, is a quantity of fundamental interest but also of a certain pragmatic interest: some sufficient knowledge of electronic structure is needed for reliable determination of the target temperature and ionization state in dense plasma and warm dense matter (WDM) experiments 25,26 , and this capability is in turn needed for campaigns to experimentally measure the EOS in the WDM regime [27][28][29] .…”

Section: Introductionmentioning

confidence: 99%

Photometric study of single-shot energy-dispersive x-ray diffraction at a laser plasma facility

Hoidn

Seidler

2014

Physics of Plasmas

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The low repetition rates and possible shot-to-shot variations in laser-plasma studies place a high value on single-shot diagnostics. For example, white-beam scattering methods based on broadband backlighter xray sources are used to determine changes in the structure of laser-shocked crystalline materials by the evolution of coincidences of reciprocal lattice vectors and kinematically-allowed momentum transfers.Here, we demonstrate that white-beam techniques can be extended to strongly-disordered dense plasma and warm dense matter (WDM) systems where reciprocal space is only weakly structured and spectroscopic detection is consequently needed to determine the static structure factor and thus the ionion radial distribution function. Specifically, we report a photometric study of energy-dispersive diffraction (ED-XRD) for structural measurement of high energy density systems at large-scale laser facilities such as OMEGA and the National Ignition Facility. We find that structural information can be obtained in single-shot ED-XRD experiments using established backlighter and spectrometer technologies.(*) Corresponding

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Real-space Green's function calculations of Compton profiles

Cited by 23 publications

References 84 publications

Finite Temperature Green’s Function Approach for Excited State and Thermodynamic Properties of Cool to Warm Dense Matter

Finite Temperature Green’s Function Approach for Excited State and Thermodynamic Properties of Cool to Warm Dense Matter

Theoretical treatments of the bound-free contribution and experimental best practice in X-ray Thomson scattering from warm dense matter

Photometric study of single-shot energy-dispersive x-ray diffraction at a laser plasma facility

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