Zintl Phase versus Covalent Metal: Chemical Bonding in Silicon Dumbbells of CaSi and CaSi.

Silicon dumbbells constitute identifiable anionic molecular species in Zintl phases and so-called covalent metals holding units with homopolar bonding inside a metallic framework. Based on electron-precise CaSi and metallic CaSi, the chemical bonding in Si units is investigated by computational quantum chemical methods considering the dual nature of the wave function. This concerted wave-vector and real space study substantiates that the Si dumbbells in CaSi can be referred to as molecular building units Si with additional metallic and ionic contributions in the solid.

Unconventional Spin State Driven Spontaneous Magnetization in a Praseodymium Iron Antimonide.

Consolidating a microscopic understanding of magnetic properties is crucial for a rational design of magnetic materials with tailored characteristics. The interplay of 3d and 4f magnetism in rare-earth transition metal antimonides is an ideal platform to search for such complex behavior. Here the synthesis, crystal growth, structure, and complex magnetic properties are reported of the new compound Pr Fe Sb as studied by magnetization and electrical transport measurements in static and pulsed magnetic fields up to 56 T, powder neutron diffraction, and Mößbauer spectroscopy.

Formation of BiIr nanoparticles in a microwave-assisted polyol process revealing the suboxide BiIrO.

Intermetallic phases are usually obtained by crystallization from the melt. However, phases containing elements with widely different melting and boiling points, as well as nanoparticles, which provide a high specific surface area, are hardly accessible such a high-temperature process. The polyol process is one option to circumvent these obstacles by using a solution-based approach at moderate temperatures.

Approximate Analytical Solutions for the Euler Equation for Second-Row Homonuclear Dimers.

This work presents a new method how to obtain approximate analytical solutions for the Euler equation for second-row homonuclear dimers. In contrast to the well-known Kohn-Sham method where a system of N nonlinear coupled differential equations must be solved iteratively, orbital-free density functional theory allows to access the minimizing electron density directly via the Euler equation. For simplified models, here, an atom-centered monopole expansion with one free parameter, solutions of the electron density can be obtained analytically by solving the Euler equation at the bond critical point.

Structural Variations and Bonding Analysis of the Rare-Earth Metal Tellurides Te ( = Ce, Pr, Sm, Gd; 0.004 ≤ δ ≤ 0.025).

Crystals of Te ( = Ce, Pr, Sm, Gd; 0.004 ≤ δ ≤ 0.025) were grown using alkali halide flux and chemical transport reactions.

Nonradiative Energy Transfer and Selective Charge Transfer in a WS/(PEA)PbI Heterostructure.

van der Waals heterostructures are currently the focus of intense investigation; this is essentially due to the unprecedented flexibility offered by the total relaxation of lattice matching requirements and their new and exotic properties compared to the individual layers. Here, we investigate the hybrid transition-metal dichalcogenide/2D perovskite heterostructure WS/(PEA)PbI (where PEA stands for phenylethylammonium). We present the first density functional theory (DFT) calculations of a heterostructure ensemble, which reveal a novel band alignment, where direct electron transfer is blocked by the organic spacer of the 2D perovskite.

Deformation Potentials: Towards a Systematic Way beyond the Atomic Fragment Approach in Orbital-Free Density Functional Theory.

This work presents a method to move beyond the recently introduced atomic fragment approximation. Like the bare atomic fragment approach, the new method is an ab initio, parameter-free, orbital-free implementation of density functional theory based on the bifunctional formalism that treats the potential and the electron density as two separate variables, and provides access to the Kohn-Sham Pauli kinetic energy for an appropriately chosen Pauli potential. In the present ansatz, the molecular Pauli potential is approximated by the sum of the bare atomic fragment approach, and a so-called deformation potential that takes the interaction between the atoms into account.

LaTe: modulated crystal structure and chemical bonding of a chalcogen-deficient rare earth metal polytelluride.

Crystals of the rare earth metal polytelluride LaTe, namely, lanthanum telluride (1/1.8), have been grown by molten alkali halide flux reactions and vapour-assisted crystallization with iodine. The two-dimensionally incommensurately modulated crystal structure has been investigated by X-ray diffraction experiments.

Equilibrium Bond Lengths from Orbital-Free Density Functional Theory.

This work presents an investigation to model chemical bonding in various dimers based on the atomic fragment approach. The atomic fragment approach is an ab-initio, parameter-free implementation of orbital-free density functional theory which is based on the bifunctional formalism, i.e.

Local conditions for the Pauli potential in order to yield self-consistent electron densities exhibiting proper atomic shell structure.

The local conditions for the Pauli potential that are necessary in order to yield self-consistent electron densities from orbital-free calculations are investigated for approximations that are expressed with the help of a local position variable. It is shown that those local conditions also apply when the Pauli potential is given in terms of the electron density. An explicit formula for the Ne atom is given, preserving the local conditions during the iterative procedure.

Efficient algorithms for Hirshfeld-I charges.

A new viewpoint on iterative Hirshfeld charges is presented, whereby the atomic populations obtained from such a scheme are interpreted as such populations which reproduce themselves. This viewpoint yields a self-consistent requirement for the Hirshfeld-I populations rather than being understood as the result of an iterative procedure. Based on this self-consistent requirement, much faster algorithms for Hirshfeld-I charges have been developed.