Search

Modern XAFS (X-ray Absorption Fine Structure) data-analysis is based on accurate multiple-scattering (MS) calculations of the X-ray absorption cross-section. In this paper, we present the inclusion and test of relativistic corrections for the multiple-scattering calculations within the GnXAS suite of programs, which is relevant to the treatment of the XAFS signals when atoms with high atomic number are contained into the system. We present a suitable strategy for introducing relativistic corrections without altering the basic structure of the programs. In particular, this is realized by modifying only the Phagen program calculating the atomic absorption cross sections and scattering t-matrices for the selected cluster. The modification incorporates a pseudo-Schrödinger Equation (SE) replacing the Dirac relativistic form. The phase-shift calculations have been put to a test in two known molecular and crystalline cases: molecular bromine Br2 and crystalline Pb. Calculations in an extended energy range have been shown to be very close to the non-relativistic case for Br2 (Br K-edge) while corrections have been found to exceed 25% for amplitude and phases of the XAFS multiple-scattering signals (Pb L3-edge). Benefits in the structural refinement using relativistic corrections are discussed for crystalline Pb at room temperature.

While the photo-emission process is inherently inelastic, in reality a closer investigation reveals that some coherence effects depending on the single photon and electron self-interference are indeed observable. All hinges on the Feynman’s rule according to which, if the same final state can be reached by different pathways, the probability for its observation is obtained by taking the modulus squared of the sum of the probability amplitudes of the various paths, leading to the mechanism of self-interference. To this purpose we review the two-slit and the usual crystal (Bragg) diffraction experiments, highlighting that in both cases the interference patterns are due to the self-interference of the single incoming photon. Guided by these two examples, we construct the photo-emission equivalent of these experimental set-up in the case of delocalized initial states and discuss their related diffraction patterns using the language of Multiple Scattering (MS) Theory. In the general case this approach shows that coherent emission from atomic sites does not necessarily require their equivalence and new MS processes with different periodicity appear compared to the case of emission from a single localized site. In particular, the cross section for photo-emission from a valence band state factorizes, like in the diffraction counterpart, into an electronic part (photo-emission from a localized atom) and a modulating Bragg factor, where the momentum exchanged with the crystal involves the initial Brillouin Zone, the impinging photon and the final photoelectron wavevectors. Photo-emission from diatomic molecules is a particular case of this general framework. We show that, when the photoelectron is detected, the coherent emission from the two atomic centers realizes the analog of the Young’s two-slit experiment, whereas in the case of photo-absorption the Cohen-Fano interference oscillations observed in the absorption cross section are to be ascribed to new MS paths joining the two sites.

We investigate the ground state and low-energy spin-orbital excitations of a single iron(II) phthalocyanine molecule in isolation and on an oxidized Cu(110) surface. Considering the subspace spanned by the three lowest spin-triplet states of 3A2g and 3Eg symmetry, we diagonalize the Hamiltonian made of the anisotropic spin-orbit interaction and the ligand field splitting Δ, defined as the energy difference between 3Eg and 3A2g. We find that the ground state switches from a 3Eg-like state with large orbital moment and out-of-plane easy axis for Δ−60 meV. The analysis of the first excited states in the two regimes explains the zero-field splitting data reported for β-FePc as well as for FePc molecules adsorbed on an oxidized Cu(110) surface [N. Tsukahara et al., Phys. Rev. Lett. 102, 167203 (2009)]. Importantly, the calculated magnetic susceptibility obtained with the ab initio value Δ=93 meV compares remarkably well with the experimental data of β-FePc in the whole available temperature range of 1–300 K., This work has been partially supported by the Spanish MAT2017-83468-R project, Aragonese E-12 17R RASMIA (co-funded by Fondo Social Europeo), and of the European Union FEDER (ES). We also acknowledge funding by the European Union COST MP1306 EUSPEC project and by the Japan Society for the Promotion of Science (JSPS), Grant KAKENHI JP 16K05393.

We determine the magnetic ground state of the FePc molecule on Au-supported thin films based on the observed values of orbital anisotropy and spectroscopic x-ray magnetic circular dichroism (XMCD) measurements at the Fe $K$ and $L$ edges. Starting from ab initio molecular orbital multiplet calculations for the isolated molecule, we diagonalize the spin-orbit interaction in the subspace spanned by the three lowest spin triplet states of ${}^{3}{A}_{2g}$ and ${}^{3}{E}_{g}$ symmetry in the presence of a saturating magnetic field at a polar angle $\ensuremath{\theta}$ with respect to the normal to the plane of the film, plus an external perturbation representing the effect of the molecules in the stack on the FePc molecule under consideration. We find that the orbital moment of the ground state strongly depends on the magnetic field direction in agreement with the sum rule analysis of the ${L}_{23}$-edge XMCD data. We calculate integrals over the XMCD spectra at the Fe $K$ and ${L}_{23}$ edges as used in the sum rules and explicitly show that they agree with the expectation values of the orbital moment and effective spin moment of the ground state. On the basis of this analysis, we can rule out alternative candidates proposed in the literature.

International audience; A brief derivation of the cross section in the independent particle approximation for some of the spectroscopies treated in the msspec program package is presented. We solve the related Schrödinger equation with a complex energy-dependent effective potential in the framework of multiple scattering theory to write the cross-section for photoemission and photoabsorption in a physically transparent way that provides insight in their interpretation and analysis. Relativistic corrections are also implemented. In order to be able to apply this theory to a wide variety of systems we use a kind of all-purpose optical potential, depending only on the local density of the system under investigation, and discuss its merits and drawbacks. A Green’s function approach is shown to be necessary to write the photoabsorption cross section in the case of complex potential. © 2018, Springer International Publishing AG, part of Springer Nature.

We show how to implement a Full Potential Multiple Scattering (fpms) code based on a real-space FPMS theory valid for both continuum and bound states, under conditions for space partitioning that are less restrictive than those applied so far. This theory is free from the need to expand cell shape functions in spherical harmonics or to use rectangular matrices. Tests of the program show that it is able to reproduce with very good accuracy known solutions of the Schrodinger equation. Applications to the spectroscopy of low dimensional systems, such as one-dimensional (1D) chain like systems, 2D layered systems and 3D diamond structure systems, where the Muffin-Tin approximation is known to give very poor results, show a remarkable improvement toward the agreement with experiments. The default mode of the code uses superimposed atomic charge densities, which works satisfactorily in most of the applications, but with help of the es2ms interface, incorporated in the program, one can also use self-consistent charge densities derived from the vasp program. The program is also incorporated in the photoelectron diffraction code msspec and parallelized for energy point.

International audience; We derive a general spherical wave multiple scattering expression of the EELS cross-section. Contrarily to most of the previous theoretical frameworks, this approach treats all the electrons involved on an equal footing with respect to multiple scattering. The main point in our results is that the cross-section depends not only on Coulomb integrals on the absorbing atom, but also on contributions from all the other atoms. We show that these external contributions should be restricted to neighbouring atoms. © 2018, Springer International Publishing AG, part of Springer Nature.

International audience; We present a scattering theoretic approach to the calculation of the cross-section of (e,2e) impact spectroscopy where all the electrons involved are treated within the real space multiple scattering framework. This approach is particularly suited to the reflection geometry at low kinetic energies, with the ejection of a core-level electron. In this case, we expect (e,2e) spectroscopy can be turned into an extremely sensitive surface structure probe. © 2018, Springer International Publishing AG, part of Springer Nature.

The experimental evidence for orbital ordering in ${\mathrm{LaMnO}}_{3}$ and ${\mathrm{La}}_{0.5}{\mathrm{Sr}}_{1.5}{\mathrm{MnO}}_{4}$ is critically reexamined in the light of realistic calculations based on multiple scattering theory and finite difference method for the resonant x-ray scattered intensity at a forbidden reflection. It is found that the dipole resonant x-ray diffraction at the Mn $K$-edge is not a suitable technique for the direct observation of the orbital ordering in the considered compounds.

A method is presented to calculate the natural circular dichroism recently discovered in the X-ray range (XNCD). The basic formula represents XNCD as an odd second-rank tensor and leads to a sum rule that relates XNCD to the mixing of odd and even orbitals in the ground state. A multiple-scattering theory of XNCD is presented, and calculated spectra for the L-edges of iodine in LiIO3 compare favorably with the experiments.

In analyzing the x-ray-absorption near-edge structure (XANES) at the La, Nd, Gd, Y, and Sr ${L}_{3}$ edges in $T$- and ${T}^{\ensuremath{'}}$-phase materials, we have found a general rule that links the presence of a feature at about 20 eV from the rising edge, called $A$ in the experimental data by Tan et al. [Phys. Rev. Lett. 64, 2715 (1990)], with the geometrical arrangement around the absorbing site. The absorption spectra of ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4},$ ${\mathrm{Nd}}_{2}{\mathrm{CuO}}_{4},$ ${\mathrm{Gd}}_{2}{\mathrm{CuO}}_{4},$ and ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}$ compounds are analyzed by full multiple-scattering theory with complex potential of Hedin-Lundqvist type obtaining very good agreement between theory and experiments. As a result of this analysis we show that feature $A$ in these spectra appears every time the photoabsorber has an eightfold hexahedron-type coordination with its nearest neighbors. This finding can be used to determine the rare-earth ordering in ${T}^{*}$-phase superconductors.

We present a theoretical analysis, based on the zeroth-order approximation of the multichannel multiple-scattering theory, of the x-ray-absorption spectra of ${\mathrm{Nd}}_{2}$${\mathrm{CuO}}_{4}$, ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$, and ${\mathrm{Ca}}_{2}$${\mathrm{CuO}}_{3}$ compounds at the copper K edge. Single-channel theoretical calculations have been made using atomic clusters large enough to be sure that all one-electron features have been correctly described. On this basis the presence of both 3${\mathit{d}}^{9}$ and 3${\mathit{d}}^{10}$L configurations in the ground state has been found essential to obtain good agreement between experimental data and theoretical calculations in the case of ${\mathrm{Nd}}_{2}$${\mathrm{CuO}}_{4}$ and ${\mathrm{Ca}}_{2}$${\mathrm{CuO}}_{3}$. Conversely, the best agreemnt with the ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$ data has been obtained by taking into account only the 3${\mathit{d}}^{10}$L configuration in the final state. We briefly comment on this finding. \textcopyright{} 1996 The American Physical Society.

We briefly discuss how to reduce the many-body problem of the photoemission (photoabsorption) process to an effective one particle problem with complex (optical) potential. By solving the associated Schrodinger equation in the framework of the multiple scattering (MS) theory, we present a unifying approach for interpreting and calculating the X-ray absorption structure (XAS), both magnetic (MCD) and nonmagnetic, and the photoelectron diffraction patterns (PhD), which are shown to be interpretable as a kind of EXAFS in three dimensions (energy plus two angles defining the photoelectron escape direction). We shall also comment on the theoretical aspects of the photoemission and photoabsorption processes that are common to both techniques and enter into a practical code of calculation of the related signals, like the muffin-tin approximation and the way to eliminate it, the effective optical potential, the photoelectron damping, the role of the intrinsic and extrinsic excitations.

We present a general multiple-scattering (MS) scheme utilizing complex potentials for the calculation and interpretation of inner-shell x-ray-absorption fine structure for clusters of atoms in condensed matter with application to the case of the molecules SF 6 , GeCl 4 , and Br 2 . The method is based on the solution of the Dyson equation with a complex self-energy of the Hedin-Lundqvist type for the single-particle Green's function describing the propagation of the excited photoelectron through the system

24 páginas, 6 figuras, 1 tabla.-- El pdf del artículo es la versión pre-print: arXiv:0809.0069v5, We present a rigorous derivation of a real-space full-potential multiple scattering theory (FP-MST) that is free from the drawbacks that up to now have impaired its development (in particular the need to expand cell shape functions in spherical harmonics and rectangular matrices), valid both for continuum and bound states, under conditions for space partitioning that are not excessively restrictive and easily implemented. In this connection we give a new scheme to generate local basis functions for the truncated potential cells that is simple, fast, efficient, valid for any shape of the cell and reduces to the minimum the number of spherical harmonics in the expansion of the scattering wavefunction. The method also avoids the need for saturating 'internal sums' due to the re-expansion of the spherical Hankel functions around another point in space (usually another cell center). Thus this approach provides a straightforward extension of MST in the muffin-tin (MT) approximation, with only one truncation parameter given by the classical relation lmax = kRb, where k is the electron wavevector (either in the excited or ground state of the system under consideration) and Rb is the radius of the bounding sphere of the scattering cell. Moreover, the scattering path operator of the theory can be found in terms of an absolutely convergent procedure in the lmax →∞ limit. Consequently, this feature provides a firm ground for the use of FP-MST as a viable method for electronic structure calculations and makes possible the computation of x-ray spectroscopies, notably photo-electron diffraction, absorption and anomalous scattering among others, with the ease and versatility of the corresponding MT theory. Some numerical applications of the theory are presented, both for continuum and bound states., CRN acknowledges financial support from DGA (Diputaci´on General de Arag´on) in the framework of the promotion action for researcher mobility. This work has been accomplished in the framework and with the support of the European Network LightNet.

Physical review / B 42(1), 37 - 42 (1990). doi:10.1103/PhysRevB.42.37, We demonstrate that texture effects can seriously distort the measurement of x-ray-absorption data from powdered specimens. We show that the isotropic average dipolar x-ray-absorption spectrum can always be measured irrespective of the degree of texture, provided axial symmetry in the particle distribution function exists normal to the specimen surface and a linearly polarized x-ray beam is employed. A simple modification to synchrotron-radiation experiments to achieve this consists of rotating the specimen by θm about an axis perpendicular to the polarization vector and beam direction from normal incidence. θm is given by sin2Θm=1/3., Published by Inst., Woodbury, NY

We present a Full Potential Multiple Scattering (FP-MS) scheme for the interpretation of several X-ray spectroscopies that is a straightforward generalization of the more conventional Muffin-Tin (MT) version. Like this latter, it preserves the intuitive description of the physical process under consideration and overcomes some of the limitations of the existing FP-MS codes. It hinges on a fast and efficient method for solving the single cell scattering problem that avoids the convergence drawbacks of the angular momentum (AM) expansion of the cell shape function and relies on an alternative derivation of the multiple scattering equations (MSE) that allows us to work reliably with only one truncation parameter, {\it i.e.} the number of local basis functions in the expansion of the global scattering function determined by the classical relation $l_{\rm max} \sim k R$., Comment: 4 pages 2 figures

We present a new scheme for solving the scattering problem for an arbitrarily shaped potential cell that avoids the well known convergence problems in the angular momentum expansion of the cell shape function. Tests of the method against analytically soluble separable model potentials, with and without shape truncation, have been performed with success. By a judicious choice of the shape of the cells partitioning the whole molecular space and use of empty cells when necessary, we set up a multiple scattering scheme that leads to a straightforward generalization of the same equations in the muffin‐tin approximation. For example lmax in the angular momentum expansion can still be chosen according to the rule lmax ∼ kR, where R is the radius of the bounding sphere of the cell and all the matrices appearing in the theory are square matrices.

We report a theoretical method for x-ray absorption spectroscopy (XAS) in condensed matter which is based on the multichannel multiple scattering theory of Natoli et al. and the eigen-channel $R$-matrix method. While the highly flexible real-space multiple scattering (RSMS) method guarantees a precise description of the single-electron part of the problem, multiplet-like electron correlation effects between the photoelectron and localized electrons can be taken account for in a configuration interaction scheme. For the case where correlation effects are limited to the absorber atom, a technique for the solution of the equations is devised, which requires only little more computation time than the normal RSMS method for XAS. The method is described and an application to XAS at the Ca ${L}_{2,3}$ edge in bulk Ca, CaO, and $\mathrm{Ca}{\mathrm{F}}_{2}$ is presented.

The experimental evidence for orbital ordering (OO) in LaMnO3 is critically reexamined in the light of realistic calculations based on finite difference method (FDM) for the resonant x-ray scattered intensity at a forbidden reflection. After some introduction on the way of calculation, it is shown that the main contribution to the scattered intensity is not due to orbital ordering but to the Jahn-Teller distortion. It is concluded that the dipole resonant x-ray diffraction at the Mn K-edge is not a suitable technique for the direct observation of the orbital ordering in the considered compounds. A short glance on the Fe3O4 compound is also given demonstrating a mixed dipolar-quadrupolar contribution in the anomalous signal.

Trabajo presentado a la 15th International Conference on X-ray Absorption Fine Structure (XAFS15), celebrada del 22 al 28 de julio de 2012 en Pekín (China).-- Licencia Creative Commons Reconocimiento 3.0, We have performed a deep spectroscopic study of incommensurate satellite reflections (h, k, l) ± (0,0.278, 0) on a TbMnO3 single crystal in order to shed light on its physical origin. Resonant x-ray scattering experiments at the Mn K-edge and Tb L3-edge have been performed at different temperatures and azimuthal angles, analyzing the outgoing light polarization. Our experimental results agree with a magnetic origin for A and C-type reflections, while F and G-type have the hallmarks of anisotropic tensor susceptibility (ATS) reflections, so that they come purely from the structural modulation., The authors thank ESRF for granting beam time, especially ID20 staff. Financial support from Spanish MICINN (project FIS08-03951 and MAT2007-61621) and DGA (CAMRADS) is acknowledged.

We present a rigorous derivation of a real space full-potential multiple-scattering theory (FP-MST), valid both for continuum and bound states, that is free from the drawbacks that up to now have impaired its development, in particular the need to use cell shape functions and rectangular matrices. In this connection we give a new scheme to generate local basis functions for the truncated potential cells that is simple, fast, efficient, valid for any shape of the cell and reduces to the minimum the number of spherical harmonics in the expansion of the scattering wavefunction. This approach provides a straightforward extension of MST in the muffin-tin (MT) approximation, with only one truncation parameter given by the classical relation l(max) = kR(b), where k is the photo-electron wavevector and R(b) the radius of the bounding sphere of the scattering cell. Some numerical applications of the theory are presented, both for continuum and bound states.

We describe the testing of a non-maffin-tin extension to the scattered-wave method (due to Natoli, Benfatto and Doniach [Phys. Rev. A 34, 4682(1986)]) for the calculation of one-electron energy eigenvalues and photoionization cross sections of molecules. For bound states the hydrogen molecular ion is used, and for continuum photoionization an ionized lithium pseudocluster is used, these being excellent tests because the analytic results are also known. Comparison of the results shows that the theory is correct and that the computational approach is feasible.

We outline a many-body description of the photoemission and photoabsorption processes that incorporates the multichannel treatment of the atomic dynamical excitations into the framework of multiple-scattering (MS) theory. This generalization is a most natural one, in that the internal structure of the atomic constituents of the physical system under study is taken into account by the introduction of an interchannel atomic t matrix that fixes the probability amplitude of a particular excitation (channel) of the internal degrees of freedom of the atom by the photoelectron impinging on it. For the rest the MS structure of the theory is left unchanged, provided the propagation vector of the photoelectron between successive scattering events is changed according to the energy loss suffered. In this way the interplay between excitation dynamics and electronic and geometrical structure of the ground state is elucidated. At the same time this approach provides a theoretical model for the study of the evolution from the adiabatic to the sudden regime. In this context we describe a new MS expansion that reproduces the results of the sudden approximation for photoemission and photoabsorption cross sections in the limit of high photoelectron energies. As expected, the expansion parameter that controls the crossover between the two regimes is substantially the maximum eigenvalue of the interchannel atomic t matrix (${\mathrm{T}}_{\mathrm{a}}$${)}_{\mathrm{LL}\ensuremath{'}}^{\mathrm{\ensuremath{\alpha}}\mathrm{\ensuremath{\alpha}}\ensuremath{'}}$(\ensuremath{\alpha}\ensuremath{\ne}\ensuremath{\alpha}\ensuremath{'}), where \ensuremath{\alpha} is a channel index and L is an angular-momentum index: If this quantity is much less than one, then the deviations from the sudden approximation are negligible. Physical applications of the theory are briefly described.

A mathematically transparent derivation of the multiple-scattering equations valid for a general non-muffin-tin potential, as applied to clusters of atoms with and without a surrounding outer sphere, is presented. These equations are shown to be a natural generalization of the analogous equations valid for muffin-tin potentials. An expression for the photoabsorption and electron scattering cross section in the framework of the multiple-scattering theory valid for a general potential is derived for what may be the first time, providing the necessary generalization for the similar expression valid in the muffin-tin case. A connection with the Green-function approach to the problem is also established via a generalized optical theorem.

We report the experimental extraction of the multiple-scattering contribution to the K-edge x-ray-absorption near-edge structure spectrum (XANES) of crystalline silicon. The multiple-scattering signal, is obtained by taking the difference ${\mathrm{\ensuremath{\chi}}}_{\mathrm{expt}}$(k)-${\mathrm{\ensuremath{\chi}}}_{2}$(k)=${\mathrm{\ensuremath{\chi}}}_{\mathrm{MS}}$(k)= where ${\ensuremath{\chi}}_{\mathrm{expt}(\mathrm{k})}$ is defined as [\ensuremath{\alpha}(k)-${\ensuremath{\alpha}}_{0}$(k)]/${\ensuremath{\alpha}}_{0}$(k), ${\ensuremath{\chi}}_{2}$ is the spherical-wave-calculated extended x-ray-absorption fine-structure (EXAFS) signal, and the ${\ensuremath{\chi}}_{n}$'s are the multiple-scattering contributions to the total absorption coefficient \ensuremath{\alpha}(k) assumed to have the form \ensuremath{\alpha}(k)=${\mathrm{\ensuremath{\alpha}}}_{0}$(k)[1+ over the full wave-vector range, ${\ensuremath{\alpha}}_{0}$(k) being the atomic absorption coefficient. The ${\ensuremath{\chi}}_{2}$ term has been calculated over the full energy range by using a spherical-wave formula and including mean-free-path and Debye-Waller effects. By using the subtraction procedure we find a ${\ensuremath{\chi}}_{\mathrm{MS}}$ oscillation of large amplitude in the first 70 eV of the spectrum. Comparison with the theoretical double scattering ${\ensuremath{\chi}}_{3}$(k) gives account of the main features of the ${\ensuremath{\chi}}_{\mathrm{MS}(\mathrm{k})}$ spectrum. We show that the main ${\ensuremath{\chi}}_{3}$ contribution comes from the double scattering paths involving atoms of the first as well as of the second shell and that higher terms of the series (ng3) are damped by the finite core hole lifetime and the inelastic losses of the photoelectron in the final state. Finally we analyze the K-edge absorption spectra of amorphous silicon. We find that the ${\ensuremath{\chi}}_{\mathrm{MS}}$ signal, contrary to the crystalline case, is suppressed. Its suppression is assigned to the orientational disorder in bond angles in the amorphous phase.

Spherical-wave corrections in x-ray-absorption fine structure (XAFS) are incorporated using a novel high-energy approximation which replaces the plane-wave approximation and is found to be in excellent agreement all the way to the absorption edge. The single-scattering theory of XAFS is recovered in terms of distance-dependent backscattering amplitudes. Application to the $K$-shell XAFS of Cu yields results in close agreement with the corresponding exact treatment. Multiple-scattering contributions in XAFS and spherical-wave corrections in angle-resolved photoemission are treated similarly.

By making a comparison between the Mn K-edge absorption of (${\mathrm{MnO}}_{4}$${)}^{\mathrm{\ensuremath{-}}}$ and [Mn(${\mathrm{H}}_{2}$O${)}_{6}$${]}^{2+}$ complexes in aqueous solution we obtain an experimental determination of the energy extent of the type-II multiple-scattering (MS) regime that is substantially wider than expected. Theoretical calculations based on the MS formalism support this conclusion. We also recognize three energy regions in the absorption spectra of these complexes: a full MS region, where numerous or an infinite number of MS paths of high order contribute (depending on whether the MS series converges or not), an intermediate MS region, where only a few MS paths of low order are relevant, and a single-scattering region where the photoelectron is backscattered only once by the ligands [extended x-ray-absorption fine-structure (EXAFS) regime]. Theoretical considerations show that this must be a general situation in x-ray-absorption spectra and opens the way to a unified scheme for their interpretation. The energy extent of the three regions is obviously system dependent. We also show how to generalize to MS contributions the usual EXAFS analysis using curved-wave propagators and indicate how to extract geometrical information from the spectra of the two clusters investigated. In particular the method is used to derive the Mn---O---O---Mn path length in the (${\mathrm{MnO}}_{4}$${)}^{\mathrm{\ensuremath{-}}}$ complex.

We present an exact and efficient method to calculate both thermal and structural damping of the multiple scattering (MS) contributions to the x-ray absorbtion coefficient. Our method, which accouts for the correlations, gives some results which indicate that only for the EXAFS signal the dominat damping is given by a simple Debye-Waller type of correction in the amplitude. In the higher order contribution to total cross section phase effects become important and can alter the effective damping. In the case of structural disorder we show how the MS signal is capable of providing new structural information in such a way to allow us to distinguish between various amorphous structural model.