TiGePt--a study of Friedel differences

The Publications of Howard Flack (1943–2017)

Howard Flack was a driving force in the development of modern crystallography. Today “the Flack parameter” has entered into the common parlance of crystallography but his influence was far wider. This article provides an overview of his scientific output and a full bibliography.

Thermal and Electronic Transport Properties of the Half-Heusler Phase ScNiSb

Thermoelectric properties of the half-Heusler phase ScNiSb (space group F 4 ¯ 3m) were studied on a polycrystalline single-phase sample obtained by arc-melting and spark-plasma-sintering techniques. Measurements of the thermopower, electrical resistivity, and thermal conductivity were performed in the wide temperature range 2-950 K. The material appeared as a p-type conductor, with a fairly large, positive Seebeck coefficient of about 240 μV K^-1 near 450 K. Nevertheless, the measured electrical resistivity values were relatively high (83 μΩm at 350 K), resulting in a rather small magnitude of the power factor (less than 1 × 10^-3 W m^-1 K^-2) in the temperature range examined. Furthermore, the thermal conductivity was high, with a local minimum of about 6 W m^-1 K^-1 occurring near 600 K. As a result, the dimensionless thermoelectric figure of merit showed a maximum of 0.1 at 810 K. This work suggests that ScNiSb could be a promising base compound for obtaining thermoelectric materials for energy conversion at high temperatures.

Chemical Bonding Analysis as a Guide for the Preparation of New Compounds: The Case of VIrGe and HfPtGe

The chemical bonding of transition metal compounds with a MgAgAs-type of crystal structure is analyzed with quantum chemical position-space techniques. The observed trends in QTAIM Madelung energy and nearest neighbor electron sharing explain the occurrence of recently synthesized MgAgAs-type compounds, TiPtGe and TaIrGe, at the boundary to the TiNiSi-type crystal structure. These bonding indicators are used to identify favorable element combinations for new MgAgAs-type compounds. The new phases-the high-temperature VIrGe and the low-temperature HfPtGe-showing this type of crystal structure are prepared and characterized by powder X-ray diffraction and differential thermal analysis.

29Si,47Ti,49Ti and195Pt solid state MAS NMR spectroscopic investigations of ternary silicides TPtSi, germanides TPtGe (T = Ti, Zr, Hf) and stannide TiPtSn

Silicides TPtSi, germanides TPtGe (T = Ti, Zr, Hf) and stannide TiPtSn show well resolved²⁹Si,⁴⁷Ti,⁴⁹Ti and¹⁹⁵Pt solid state MAS NMR spectra.

Patterson functions

The paper deals with |F|2, A and D Patterson functions. The information available in the various volumes of International Tables for Crystallography is detailed. A and D are defined and the reason for their use is explained. The symmetry of these functions is explained. Calculation by symmetry-adapted Patterson functions and the Fast-Fourier algorithm are described. There are two examples. There is a very useful table presenting the relevant information.