Synchrotron powder X-ray diffraction data are used to determine the core electron deformation of diamond. Core shell contraction inherently linked to covalent bond formation is observed in close correspondence with theoretical predictions. Accordingly, a precise and physically sound reconstruction of the electron density in diamond necessitates the use of an extended multipolar model, which abandons the assumption of an inert core. The present investigation is facilitated by negligible model bias in the extraction of structure factors, which is accomplished by simultaneous multipolar and Rietveld refinement accurately determining an atomic displacement parameter (ADP) of 0.00181 (1) Å(2). The deconvolution of thermal motion is a critical step in experimental core electron polarization studies, and for diamond it is imperative to exploit the monatomic crystal structure by implementing Wilson plots in determination of the ADP. This empowers the electron-density analysis to precisely administer both the deconvolution of thermal motion and the employment of the extended multipolar model on an experimental basis.

Several efficient thermoelectric materials have been found among the ternary Zintl antimonides. If the band structure is highly asymmetric around the band gap, the efficiency as either n- or p-type may differ significantly. The Zintl antimonides have generally been found to be p-type. Surprisingly, this also holds true for the narrow band gap binary ZnSb and Zn4Sb3. Using ab initio calculations, we investigate intrinsic point defects in ZnSb as a possible origin of the p-type conductivity. Only Zn vacancies are found to be present in significant amounts at room temperature. The low formation energy of negatively charged Zn defects pins the electronic chemical potential to the lower part of the band gap leading to intrinsic ZnSb being p-type. We discuss this finding as a general explanation of p-type conductivity in Zintl antimonides, and how to overcome the doping limits in these materials.

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The chemical bonding in the pyrite (left) and marcasite (right) polymorphs of FeS2is investigated by charge density analysis.

Zinc antimonides are interesting as thermoelectric materials, since their constituents are relatively cheap and abundant, and a number of compounds have exhibited good thermoelectric figures of merit. This paper focuses on theoretical studies of BaZn2Sb2, CaZn2Sb2, and ZnSb using density functional theory. In all compounds, a gap at the Fermi level is found which can be rationalized using the Zintl–Klemm principle. On the basis of electronic structure calculations, the transport properties are calculated using Boltzmann transport theory. BaZn2Sb2 as both p and n-type is found to have favorable properties along the b-axis. ZnSb was predicted to have favorable thermoelectric properties as n-type. Minima in the lowest conduction band in ZnSb are rationalized as stemming from increased bonding between distant neighbors at special k-points. By comparing the calculated transport properties to experimental measurements from literature, the carrier concentrations, band gaps, and relaxation times of the compounds are determined and the relevance of a constant κ l /τ approximation is discussed.