RESUMEN
We report the synthesis and characterization of Fe0.36(4)Pd0.64(4)Se2 with a pyrite-type structure. Fe0.36(4)Pd0.64(4)Se2 was synthesized using ambient pressure flux crystal growth methods even though the space group Pa3 is high-pressure polymorph for both FeSe2 and PdSe2. Combined experimental and theoretical analysis reveal magnetic spin glass state below 23 K in 1000 Oe that stems from random Fe/Pd occupancies on the same atomic site. The frozen-in magnetic randomness contributes significantly to electronic transport. Electronic structure calculations confirm dominant d-electron character of hybridized bands and large density of states near the Fermi level. Flux-grown single crystal alloys in Pd-Fe-Se atomic system therefore open new pathway for exploring different polymorphs in crystal structures and their novel properties.
RESUMEN
X-ray absorption spectroscopy is employed to investigate site preference and lattice relaxation around Mo, Ru, Hf, W and Re dopants in Ni3Al. The site occupation preference and the measured distances between the refractory elements as dopants and the nearest host atoms are compared with the results of ab initio calculations within the density functional theory. Combined experimental and theoretical results indicate that Mo, Hf, W and Re atoms reside on the Al sublattice in Ni3Al, while Ru atoms occupy the Ni sublattice. A more pronounced lattice relaxation was detected in the case of Hf and Ru doping, with a strong outward relaxation of the nearest Ni and Al atoms.
RESUMEN
Mg2FeH6 is a promising hydrogen storage material with one of the highest volumetric hydrogen density among the known hydrogen storage materials. However, its complicated synthesis and high temperature of hydrogen desorption limit wider applications. In this paper we study the influence of transition metal (Ni, Co, Mn) doping on the structural, electronic and hydrogen sorption properties of Mg2FeH6, using first-principles density functional theory calculations. The thermodynamics of three different synthesis routes is addressed, and all of the mentioned transition metals are found to destabilize Mg2FeH6. In addition, a detailed study of electronic structure properties, including densities of states (DOS) and charge transfer analysis (AIM), reveals that the doping with Ni, Mn and Co leads to the reduction of the direct band gap of Mg2FeH6.
RESUMEN
The lattice relaxation around Ga in CdTe is investigated by means of extended X-ray absorption spectroscopy (EXAFS) and density functional theory (DFT) calculations using the linear augmented plane waves plus local orbitals (LAPW+lo) method. In addition to the substitutional position, the calculations are performed for DX- and A-centers of Ga in CdTe. The results of the calculations are in good agreement with the experimental data, as obtained from EXAFS and X-ray absorption near-edge structure (XANES). They allow the experimental identification of several defect structures in CdTe. In particular, direct experimental evidence for the existence of DX-centers in CdTe is provided, and for the first time the local bond lengths of this defect are measured directly.