Although known since the late 19th century, organic–inorganic perovskites have recently received extraordinary research community attention because of their unique physical properties, which make them promising candidates for application in photovoltaic (PV) and related optoelectronic devices. This review will explore beyond the current focus on three-dimensional (3-D) lead(II) halide perovskites, to highlight the great chemical flexibility and outstanding potential of the broader class of 3-D and lower dimensional organic-based perovskite family for electronic, optical, and energy-based applications as well as fundamental research. The concept of a multifunctional organic–inorganic hybrid, in which the organic and inorganic structural components provide intentional, unique, and hopefully synergistic features to the compound, represents an important contemporary target.

Organic–Inorganic Perovskites: Structural Versatility for Functional Materials Design

Accurate estimates of the magnetic coupling in binuclear complexes can be obtained from ab initio configuration interaction (CI) calculations using the difference dedicated CI technique. The present paper shows that the same technique also provides a way to analyze the various physical contributions to the coupling and performs numerical analysis of their respective roles on four binuclear complexes of Cu (d9) ions. The bare valence-only description (including direct and kinetic exchange) does not result in meaningful values. The spin-polarization phenomenon cannot be neglected, its sign and amplitude depend on the system. The two leading dynamical correlation effects have an antiferromagnetic character. The first one goes through the dynamical polarization of the environment in the ionic valence bond forms (i.e., the M+⋯M− structures). The second one is due to the double excitations involving simultaneously single excitations between the bridging ligand and the magnetic orbitals and single excitations of...

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Analysis of the magnetic coupling in binuclear complexes. I. Physics of the coupling

Modern techniques of liquid state physics have been successfully used to probe the microscopic structure and dynamics of a variety of multicomponent liquids in which relative ordering of the species is present near freezing. The alkali halides are prototypes for this specific type of short-range order in relation to the nature of bonding, but the systems in question also include other monovalent and polyvalent metal-ion halides, alkali-based intermetallic compounds and chalcogen-based alloys. A viewpoint is taken in this review which gives attention to the relations between liquid and solid phase properties across melting for compound systems at stoichiometric composition. In addition, large deviations for stoichiometry can be realised in the liquid phase, to display trends of evolution of structure, bonding and electronic states with composition.

https://iopscience.iop.org/article/10.1088/0034-4885/49/9/002/pdf

Structure and dynamics of molten salts

Nonlinear diffusion and phase separation

Magnetic light scattering in low-dimensional quantum spin systems

A mechanism is suggested which can modify in certain cases the Goodenough-Kanamori-Anderson rules determining the character of superexchange in magnetic insulators; namely, side groups coupled to ligands, which are often present but are usually ignored, may contribute significantly, and may in certain cases even lead to a change in sign of the superexchange interaction. Thus this factor can make the 90\ifmmode^\circ\else\textdegree\fi{} superexchange of half-filled shells antiferromagnetic, in contrast to the usual case. Qualitative arguments and numerical estimates show that this mechanism may be important in the inorganic spin-Peierls compound ${\mathrm{CuGeO}}_{3}$. \textcopyright{} 1996 The American Physical Society.

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Influence of side groups on 90 degrees superexchange: A modification of the Goodenough-Kanamori-Anderson rules.

Neutron diffraction measurements of liquid Na-Sn alloys provide evidence for appreciable ordering in the liquid. At small Sn concentrations (about 20 at.%) the liquid is similar to a simple ionic mixture with maximum distance between the negatively charged Sn atoms. At higher Sn concentrations, the Sn atoms tend to form aggregates, perhaps in the form of tetrahedra of covalently bonded Sn atoms. Elements of the solid structure seem to be preserved in the liquid state.

https://iopscience.iop.org/article/10.1088/0305-4608/13/12/007/pdf

Structure of liquid Na-Sn alloys

This paper deals with a number of selected topics from the field of electric transport properties in liquid metals and alloys. First, some nearly free electron systems are considered; it appears that some problems associated with the properties of liquid Na–Cs alloys and of amalgams are still unsolved. Then, systems exhibiting strong compound formation, particularly alkali–nonalkali alloys with a large electronegativity difference between the components, are reviewed. A qualitative interpretation in terms of chemical-valence rules, based upon our knowledge of the solid state, is given. Next, recently developed theories dealing with transport properties in disordered media are critically discussed. Some models for the interpretation of the alkali – group IV alloys are presented. The basic ideas derived from these models are used also as guidelines for a more qualitative discussion of the alkali – group III and alkali – group V alloy systems.

Electron-transport in liquid-metals and alloys

In this paper the authors apply model tight-binding calculations to the electronic structure of systems in which there are essentially two covalent interactions: the intracluster interaction U and the intercluster interaction V. The atomic structure is simulated by a modified Bethe lattice which incorporates closed loops as a possibility. The ratio alpha =V/U is an important parameter to be varied. At a distinct value, alpha crit, a metal-non-metal transition takes place. The results are applied to the electronic structure and chemical stability of anion cluster in liquid and solid alkali-group-IV alloys. The physical parameters which govern the process of clustering are discussed.

Electronic structure and charge-transfer-induced cluster formation in alkali-group-IV alloys

The 7Li Knight shift has been measured in liquid Li-Pb and Li-Sn alloys through the entire concentration range and at several temperatures. The Knight shifts in liquid Li-Pb are discussed together with the electrical conductivity and the spin-lattice relaxation time T1, which also exhibit anomalous behaviour near the composition Li4Pb. The results support the assumption of a partially salt-like mixture around the composition Li4Pb.

W. Geertsma

Papers

Influence of side groups on 90 degrees superexchange: A modification of the Goodenough-Kanamori-Anderson rules.

Structure of liquid Na-Sn alloys

Electron-transport in liquid-metals and alloys

Electronic structure and charge-transfer-induced cluster formation in alkali-group-IV alloys

7Li Knight shift of liquid Li-Pb and Li-Sn alloys