The modern version of the KKR (Korringa–Kohn–Rostoker) method represents the electronic structure of a system directly and efficiently in terms of its single-particle Green's function (GF). This is in contrast to its original version and many other traditional wave-function-based all-electron band structure methods dealing with periodically ordered solids. Direct access to the GF results in several appealing features. In addition, a wide applicability of the method is achieved by employing multiple scattering theory. The basic ideas behind the resulting KKR-GF method are outlined and the different techniques to deal with the underlying multiple scattering problem are reviewed. Furthermore, various applications of the KKR-GF method are reviewed in some detail to demonstrate the remarkable flexibility of the approach. Special attention is devoted to the numerous developments of the KKR-GF method, that have been contributed in recent years by a number of work groups, in particular in the following fields: embedding schemes for atoms, clusters and surfaces, magnetic response functions and anisotropy, electronic and spin-dependent transport, dynamical mean field theory, various kinds of spectroscopies, as well as first-principles determination of model parameters.

https://iopscience.iop.org/article/10.1088/0034-4885/74/9/096501/pdf

Calculating condensed matter properties using the KKR-Green's function method—recent developments and applications

Structural characterization of noncrystalline solids and glasses using solid state NMR

Although the majority of glasses in use in technology are complex mixtures of oxides or chalcogenides, there are numerous examples of pure substances-'glassformers'-that also fail to crystallize during cooling. Most glassformers are organic molecular systems, but there are important inorganic examples too, such as silicon dioxide and elemental selenium (the latter being polymeric). Bulk metallic glasses can now be made; but, with the exception of Zr50Cu50 (ref. 4), they require multiple components to avoid crystallization during normal liquid cooling. Two-component 'metglasses' can often be achieved by hyperquenching, but this has not hitherto been achieved with a single-component system. Glasses form when crystal nucleation rates are slow, although the factors that create the slow nucleation conditions are not well understood. Here we apply the insights gained in a recent molecular dynamics simulation study to create conditions for successful vitrification of metallic liquid germanium. Our results also provide micrographic evidence for a rare polyamorphic transition preceding crystallization of the diamond cubic phase.

Vitrification of a monatomic metallic liquid

Relativistic effects, in particular the spin-orbit coupling, give rise for magnetic systems to a great number of interesting and technologically important phenomena. The formal and technical aspects of corresponding fully relativistic theoretical investigations are reviewed. The properties of the underlying Dirac equation, set up within the framework of density functional theory (DFT) are discussed together with the Breit-interaction and Brooks’ orbital polarization mechanism. As an example for a corresponding band structure method, the Korringa-Kohn-Rostoker (KKR) Green’s function method is adopted. In particular, some technical aspects specific to this technique are discussed. The numerous applications that will be presented are primarily meant to demonstrate the many different facets of relativistic - this means in general - of spin-orbit induced effiects in magnetic solids. In addition, these also demonstrate the tremendous flexibility of band structure schemes based on the Green’s function formalism.

Fully Relativistic Band Structure Calculations for Magnetic Solids - Formalism and Application

Structure and phase transformation behaviour of electroless Ni-P composite coatings

A comprehensive study of the magnetic properties of ${\mathrm{Ni}}_{100\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{P}}_{\mathit{x}}$ alloys prepared by electrodeposition with 11.5\ensuremath{\le}x\ensuremath{\le}23.2 and by melt quenching with 16.3\ensuremath{\le}x\ensuremath{\le}21.0 was performed for temperatures 4.2\ensuremath{\lesssim}T\ensuremath{\le}300 K in magnetic fields up to H=9 kOe and, for most of the melt-quenched alloys, for T\ensuremath{\ge}300 K including the molten state as well. The individual contributions to the magnetization were identified and determined separately. The matrix of Ni-P alloys was found to exhibit Pauli paramagnetism for x\ensuremath{\gtrsim}17 and very weak itinerant ferromagnetism for x\ensuremath{\lesssim}14. However, magnetic inhomogeneities in the form of ferromagnetic precipitates, giant-moment paramagnetic clusters and/or superparamagnetic particles could be identified throughout the whole concentration range studied and their amount and character varied significantly with alloy composition and preparation technique. In the paramagnetic phase, the temperature-independent Pauli susceptibility was not sensitive to the way of preparation, it agreed well with extrapolated room-temperature liquid-state data, decreased approximately linearly with increasing P content and extrapolated to the corresponding value of the crystalline stoichiometric compound ${\mathrm{Ni}}_{3}$P. In the ferromagnetic phase, the magnetization data of the matrix could be reasonably well accounted for in terms of the Stoner-Edwards-Wohlfarth model and the theory of Mathon, yielding 85.7 at. % Ni as the critical concentration for the onset of spontaneous magnetic order. For alloys in the intermediate composition range (14\ensuremath{\lesssim}x\ensuremath{\lesssim}17), the observed magnetization was dominated by the contribution of superparamagnetic particles.

Magnetic properties of electrodeposited, melt-quenched, and liquid Ni-P alloys.

Diamagnetic susceptibility of pure metals and binary alloys

The residual electrical dc resistivity of the transition-metal-alloy system Cu-Pt is evaluated by making use of the relativistic version of the Korringa-Kohn-Rostoker--coherent potential approximation and the one-electron Kubo-Greenwood formula for disordered systems. Starting from the results of a previous calculation the influence of truncation of the angular momentum expansion, the effects of self-consistency of the alloy potential, the importance of vertex corrections, and the difference between the nonrelativistic and the relativistic current operator are examined.

Approximations made in evaluating the residual electrical dc resistivity of disordered alloys

The crystallization characteristics of melt-quenched (MO) NiP amorphous alloys were studied for phosphorus contents ranging from 16.5 at.% to 21.0 at.% by differential scanning calorimetry (DSC) and by thermomagnetic analysis (TMA). The overall crystallization scheme of MQ NiP alloys was found to be similar to that obtained previously for electrodeposited (ED) NiP alloys. However, it was found that for amorphous NiP alloys with P ??? 19.5 at.%, the first transformation temperature (precipitation of nickel) differs markedly for ED and MQ alloys owing to the different chemical inhomogeneities introduced by the preparation techniques. The appearance of such chemical inhomogeneities upon annealing well below the crystallization could be sensitively detected by magnetic measurements.

Magnetic susceptibility and DSC study of the crystallization of melt-quenched NiP amorphous alloys

The thermodynamic conditions for establishing metastable crystalline solutions in AgPt alloys by quenching from the melt were studied using Hardy's subregular ansatz for the excess free enthalpy of mixing. Splat cooling experiments were performed for various concentrations and the samples were examined by X-ray diffraction. The measured lattice parameters were compared with those reported by other workers.

J. Voitländer

Papers

Magnetic properties of electrodeposited, melt-quenched, and liquid Ni-P alloys.

Diamagnetic susceptibility of pure metals and binary alloys

Approximations made in evaluating the residual electrical dc resistivity of disordered alloys

Magnetic susceptibility and DSC study of the crystallization of melt-quenched NiP amorphous alloys

Metastable solid solutions in AgPt alloys