A study of defect structures in Fe-alloyed ZnO: Morphology, magnetism, and hyperfine interactions

In order to study the effect of Fe cation substitution on the local structure, defect formation, and hyperfine interactions in ZnO, Mössbauer spectroscopy measurements of the microwave processed Zn1−xFexO (x=0.05, 0.10, 0.15, and 0.20) nanoparticles, together with ab initio calculations, were performed. Complementary information on the distribution of particle size and morphology, as well as magnetic properties, were obtained by X-ray diffraction, transmission electron microscopy, and squid-magnetometry. The selected model for analyzing the Mössbauer spectra of our samples is a distribution of quadrupole splittings. The fitting model with two Lorentz doublets was rejected due to its failure to include larger doublets. The Fe3+ ions do not yield magnetic ordering in the samples at room temperature. The results from first-principles calculations confirm that the major component of the Mössbauer spectra corresponds to the Fe-alloyed ZnO with Zn vacancy in the next nearest neighbor environment. The magnetic measurements are consistent with the description of the distribution of iron ions over the randomly formed clusters in the ZnO host lattice. While at room temperature all the samples are paramagnetic, magnetic interactions cause a transition into a cluster spin-glass state at low temperatures

Enhancing photocatalytic properties of rutile TiO2 by codoping with N and metals - Ab initio study

Substitutional N to O and M to Ti (M = Pt, V, Sb) codoped rutile TiO2 was investigated using density functional theory (OFT) based calculations with both standard and hybrid exchange-correlation functionals. The band gaps calculated using generalized gradient approximation (GGA) exhibited narrowing compared to the pure rutile TiO2 in all the investigated cases. In contrast, the results obtained with hybrid exchange-correlation functional showed that there was no band gap narrowing, but doping induced localized states within the band gap just above the valence band, as well as below the conduction band for Pt doped TiO2. The presence of broad intermediate states (IS) in the band gap could enhance visible light absorption through a two step optical transition from the valence to the conduction band via the IS and at the same time lower recombination of the photo-generated charges. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved

A Three - Detector High Resolution TDPAC Spectrometer

An advanced fast-slow coincidence scintillation spectrometer for the Timx Differential Perturbed y-y Angular Correlation (TDPAC) experiments is presented. It consists of three detectors with BaF2 scintillators and was developed in the Group for Hyperfine Interactions in the Institute for Nuclear Sciences in Vinca. The spectrometer is characterized with high detection efficiency, excellent time resolution, high counting rate performance and is operating in the temperature range 78-1300 K

Structural deformation in Hf2Ni observed by TDPAC method

The electric quadrupole interaction in Hf2Ni was measured at 181Ta probe using the time-differential perturbed angular correlation method (TDPAC) in the temperature range 78 to 1314 K. Analysis of the obtained spectra revealed the presence of a single nuclear quadrupole interaction (NQI) and its linear descending dependence with increasing temperature. In the region 1134 to 1314 K, the presence of structural deformation is evident from the coincidence spectra.YUCOMAT 2007 : 9th Annual Conference YUCOMAT 2007 : Programme and the book of abstracts; September 10-14, 2007; Herceg Novi, Montenegr

Hyperfine interactions at 181Ta solute in ferromagnetic Hf-Ni alloys with low concentration of Hf atoms

We have measured hyperfine interactions of 181Ta probe in the polycrystalline 0.2at.%Hf-Ni, 2at.%Hf-Ni and 5at.%Hf-Ni alloys, by the time differential perturbed angular correlation (TDPAC) method at room temperature (RT). The hyperfine magnetic field (Hhf) in 0.2at.%Hf-Ni alloy at the 181Ta probe is 8.66(1)T, where the small atomic concentrations of Hf atoms mainly substitute on Ni host lattice sites. Three hyperfine interactions were detected in two other alloys. In the 2at.%Hf-Ni alloy, we found existence of Larmor precession frequency ωL (1)=536(2)Mrad/s at the 181Ta probe surrounded by Ni atoms and the second electric quadrupole interaction (EQI) ωQ (2)=2.20(2)Mrad/s at the 181Ta probe in new formed HfNi5 intermetallic phase. The third EQI ωQ (3)=137.4(1)Mrad/s corresponds to the small amount of monoclinic HfO2 phase contamination at T<900K. In the 5at%Hf-Ni alloy, magnetic dipole interaction (MDI) at the 181Ta probe is ωL (1)=536(6)Mrad/s, while the second EQI at the site of the same probe in HfNi5 is ωQ (2)=2.24(2)Mrad/s. The presence of ωQ (3)=128(1)Mrad/s at the 181Ta probe originating from HfO2 contamination is in good accordance with earlier published results for this phase.52. konferencija ETRAN-a : Jun 8-12, Palić, 2008

Hyperfine interactions at 181Ta solute in ferromagnetic Hf-Ni alloys with low concentration of Hf atoms

We have measured hyperfine interactions of 181Ta probe in the polycrystalline 0.2at.%Hf-Ni, 2at.%Hf-Ni and 5at.%Hf-Ni alloys, by the time differential perturbed angular correlation (TDPAC) method at room temperature (RT). The hyperfine magnetic field (Hhf) in 0.2at.%Hf-Ni alloy at the 181Ta probe is 8.66(1)T, where the small atomic concentrations of Hf atoms mainly substitute on Ni host lattice sites. Three hyperfine interactions were detected in two other alloys. In the 2at.%Hf-Ni alloy, we found existence of Larmor precession frequency ωL (1)=536(2)Mrad/s at the 181Ta probe surrounded by Ni atoms and the second electric quadrupole interaction (EQI) ωQ (2)=2.20(2)Mrad/s at the 181Ta probe in new formed HfNi5 intermetallic phase. The third EQI ωQ (3)=137.4(1)Mrad/s corresponds to the small amount of monoclinic HfO2 phase contamination at T<900K. In the 5at%Hf-Ni alloy, magnetic dipole interaction (MDI) at the 181Ta probe is ωL (1)=536(6)Mrad/s, while the second EQI at the site of the same probe in HfNi5 is ωQ (2)=2.24(2)Mrad/s. The presence of ωQ (3)=128(1)Mrad/s at the 181Ta probe originating from HfO2 contamination is in good accordance with earlier published results for this phase.52. konferencija ETRAN-a : Jun 8-12, Palić, 2008

Enhanced superconductivity and electron correlations in intercalated ZrTe3

Charge density waves (CDWs) with superconductivity, competing Fermi surface instabilities, and collective orders have captured much interest in two-dimensional van der Waals (vdW) materials. Understanding the CDW suppression mechanism, its connection to the emerging superconducting state, and electronic correlations provides opportunities for engineering the electronic properties of vdW heterostructures and thin-film devices. Using a combination of the thermal transport, x-ray photoemission spectroscopy, Raman measurements, and first-principles calculations, we observe an increase in electronic correlations of the conducting states as the CDW is suppressed in ZrTe3 with 5% Cu and Ni intercalation in the vdW gap. As superconductivity emerges, intercalation brings not only decoupling of quasi-one-dimensional conduction electrons with phonons as a consequence of intercalation-induced lattice expansion but also a drastic increase in Zr2+ at the expense of Zr4+ metal atoms. These observations not only demonstrate the potential of atomic intercalates in the vdW gap for ground-state tuning but also illustrate the crucial role of the Zr metal valence in the formation of collective electronic orders

D7.3 - Data Management Plan

This document describes the initial version of the Data Management Plan (DMP) for the WaPoDe project. The overall objective of the WaPoDe project is to synthetize materials with enhanced sensitivity, selectivity, and response time as electrochemical sensors (ECS) for detection and monitoring of different pharmaceutical and pesticide pollutants in water and to reduce ECS manufacturing costs. The focus of the WaPoDe project is on ZnO-based electrochemical sensors. The database will be developed under the WaPoDe project with the main purpose to summarize the WaPoDe research results on the types, properties, and application of ZnO-based nanoparticles as selective ECS. This initial DMP provides information on the data management principles that will be implemented during and for a certain period after the WaPoDe project completion. It is based on the Data Management Plan template (https://enspire.science/wp-content/uploads/2021/09/Horizon-Europe-Data-Management-Plan-Template.pdf) which follows the guidelines from Europe Horizon calls. This DMP will be regularly updated as the implementation of the project progresses. The draft DMP was developed within the project workpackages

Improving the photocatalytic activity of tetragonal BiVO4 with zircon-type structure through W doping; Ab initio calculations

In this paper we studied the effects of the concentration of W as a doped atom on the V lattice site on the electronic and optical properties of tetragonal zircon-type BiVO4 structure. The calculations were performed by the first-principles density functional theory WIEN2k code. The doping strategy was targeting V atoms substituted by W atoms using the same lattice parameters as pure BiVO4 structure. To avoid the self interaction of impurities, the supercell method was adopted ensuring a sufficient length between the impurities in all directions. For all considered concentrations, the optical properties in the visible light range of λ≥550nm are improved over the undoped BiVO4. © 2021 Elsevier B.V

Ab initio calculations of the structure, energetics and stability of AunTi (n=1-32) clusters

The stability and structure of titanium doped gold clusters (AunTi; n = 1-32) are studied by density functional theory calculations, as implemented in the first principles code SIESTA. The exchange and correlation effects were calculated within the generalized gradient approximation (GGA) parametrized by Perdew, Burke and Ernzerhof (PBE). We used norm conserving Troullier-Martins pseudopotentials for the 10-electron valence configuration of Ti and 11-electron valence configuration of Au. All calculations were spin-polarized. The global energy minimum geometries of the clusters were searched for by using the simulated annealing technique. The stability of the clusters is discussed on the basis of the binding energy per atom, second-order energy difference, vertical ionization potential, vertical electron affinities, HOMO-LUMO energy gap and vibrational frequencies. Based on the simultaneous criteria of high binding energy, high band gap, high vertical ionization potential, and low electron affinity, it is found that Au4Ti and Au14Ti clusters have a higher stability and are candidates for magic clusters, which confirms the already known results from previous works. The new result presented in this paper is that the Au20Ti and Au30Ti clusters have a higher stability too. In general, the clusters with even n are more stable than the clusters with odd n. Most of the clusters with even n are non-magnetic (total magnetic moment is zero). Our results also suggest that only the Au3Ti, Au7Ti and Au8Ti clusters have a planar structure. (C) 2016 Elsevier B.V. All rights reserved