The Molybdenum rich ternary alloys Mo-M-B (M = Zr, Hf) contain, next to the Mo solid solution (bcc Mo with small amounts of Zr or Hf as substitutional atoms), the binary borides Mo₂B, MB and MB₂. Recently, it was found that there is also ternary Mo₂MB₂, but the crystal structure and further properties are currently unknown. Density functional theory (DFT) calculations were used not only to predict the crystal structure of the Mo₂MB₂ phases, but also to estimate the isotropic and anisotropic elastic properties like bulk, shear and Young’s modulus, as well as the Vickers hardness of these new borides. Several known crystal structures that fulfill the criterion of the chemical composition were investigated, and the AlMn₂B₂ type structure seems to be the most stable crystal structure for Mo₂HfB₂ and Mo₂ZrB₂ as there are no signs of electronic or dynamic instability. Regarding the elastic properties, it was found that Mo₂HfB₂ shows higher elastic moduli and is less elastically anisotropic than Mo₂ZrB₂.

Investigations in the ternary system Eu–Al–Pt led to the discovery of Eu₄Al₁₃Pt₉, a new representative exhibiting a coloring variant of the Ho₄Ir₁₃Ge₉ type structure. The orthorhombic structure was refined based on single crystal X-ray diffraction data (Pmmn, Wyckoff sequence e ⁹ b ³ a ⁵, a = 415.38(1), b = 1149.73(2), c = 1994.73(5) pm, wR2 = 0.0622, 1901 F ² values, 88 variables) and full atomic ordering was observed for all atoms. The structure features a complex [Al₁₃Pt₉] ^δ– network with the Eu atoms occupying hexagonal prismatic cavities. The bonding situation of this new platinide was investigated via quantum-chemical calculations. According to Density Functional Theory (DFT) the title compound has to be described as a polar intermetallic material with a covalently bonded [Al₁₃Pt₉] ^δ– polyanion showing strong Pt–Al alongside weak Al–Al and Pt–Pt bonding and Eu cations in the cavities.

Mo-Ti-Si, Mo-Zr-B, and Mo-Hf-B are promising alloy systems for high-temperature applications as they show higher toughness and higher creep resistance than other Mo-based alloys. Regarding ductility and toughness, the chemical composition of the Mo solid-solution phase is the main parameter with which to tweak these properties of multiphase Mo-based alloys. Besides the common solid-solution hardening, one goal is to minimize embrittlement by decreasing the detrimental effects of interstitials like oxygen atoms in Mo alloys, which might be present in the bulk material due to trapping. For a better understanding of the trapping mechanisms and behavior of Mo solid solutions, the bonding situation and interaction of Mo atoms with the atoms of the alloying partners, as well as oxygen atoms, is worthwhile to investigate. For this, an in-depth analysis of the chemical bonding situation with calculations based on density functional theory in selected Mo-TM(-O) (TM = Ti, Zr, Hf) solid solutions is conducted in this work. It is shown that Ti atoms in a Mo solid solution are strong traps for oxygen atoms, while Hf and, even more clearly, Zr atoms are not. It is pointed out that the ionic and covalent interactions are the primary influence on the trapping behavior, as the change in ionic and covalent interactions between trapping and nontrapping models follows the trend Mo-1Ti > Mo-1Hf > Mo-1Zr, which resembles the trend of the trapping energy.

In the present work the solidification of various Mo-Ti-B alloys was studied. The alloy compositions were chosen in the direct vicinity of a U-type invariant reaction in relation to the published Mo-rich corner of the Mo-Ti-B liquidus projection. The aim of this study was to understand the solidification path of as-cast Mo-Ti-B alloys and to derive specific knowledge on their peritectic microstructure evolution. In addition to experiments in an arc-melter, zone melting was used to allow slow cooling of a selected alloy composition. Using the achieved experimental data of the alloys investigated, DFT-calculations were carried out to study the influence of Ti on phase formation and stability, their lattice parameters, and mechanical properties.