%0 journal article %@ 1359-6462 %A Shang, Y.,Santhosh, A.,Jerabek, P.,Klassen, T.,Pistidda, C. %D 2024 %J Scripta Materialia %N %P 115837 %R doi:10.1016/j.scriptamat.2023.115837 %T First-principles study on interfacial property in MgB2-based reactive hydride composites %U https://doi.org/10.1016/j.scriptamat.2023.115837 %X The underlying physico-chemical interactions between transition metal-based boride particles that formed during the dehydrogenation process and MgB2 in 2LiBH4+MgH2 reactive hydride composite at the atomic scale are still unknown. In this work, the properties of the TiB2/MgB2 interface were investigated by first-principles calculations utilizing density functional theory (DFT). Taking the two terminations of both MgB2 and TiB2 as well as four different stacking sequences into account, energies of the TiB2 and MgB2 (0001) surfaces as well as the work of adhesion and the electronic structure of the interfaces were studied. The results show that the interface between the B-terminated MgB2 (0001) surface and the Ti-terminated TiB2 (0001) surface is the energetically most favorable among all four stacking options and possesses the largest work of adhesion. Our results further show that the TiB2 particles possess good nucleation potency for MgB2 particles from the thermodynamic perspective. %0 journal article %@ 2590-1230 %A Le, T.,Santhosh, A.,Bordignon, S.,Chierotti, M.,Jerabek, P.,Klassen, T.,Pistidda, C. %D 2023 %J Results in Engineering %N %P 100895 %R doi:10.1016/j.rineng.2023.100895 %T Experimental and computational studies on the formation of mixed amide-hydride solid solutions for CsNH2–CsH system %U https://doi.org/10.1016/j.rineng.2023.100895 %X In this study, experimental determination and computational prediction are combined to investigate the formation of a mixed amide-hydride solid solution for the CsNH2–CsH system in a wide compositional range. The experimentally obtained results strongly indicate that a complete amide-hydride solid solution Cs(NH2)xH1-x with a stable cubic structure is achievable when the molar fraction of amide (x) is lower than 0.9. These results validate and confirm our data computationally via first-principles calculations, including the simulations of infrared (IR) and nuclear magnetic resonance (NMR) spectra for structures of various compositions as well as the determination of the dipolar coupling constants. Both the computed vibrational frequencies and 1H chemical shifts of CsNH2 and CsH moieties in the Cs(NH2)xH1-x (x = 0.2, 0.5, 0.8, 1) solid solution structures agree with the experimental IR and 1H MAS NMR data of the mixed xCsNH2+(1-x)CsH samples, confirming the formation of the solid solutions. The closest interproton distance in the homogeneous Cs(NH2)0·5H0.5 solid solution is computed to be 3.67 Å, which is larger than that of the known Rb(NH2)0·5H0.5 solid solution (3.29 Å). This work's combination of theoretical research and experimentation provides a suitable framework for the structural analysis and property estimation of other M-N-H solid solutions. %0 journal article %@ 2050-7488 %A Santhosh, A.,Kang, S.,Keilbart, N.,Wood, B.C.,Klassen, T.,Jerabek, P.,Dornheim, M. %D 2023 %J Journal of Materials Chemistry A %N %P 18776-18789 %R doi:10.1039/D3TA02205F %T Influence of near-surface oxide layers on TiFe hydrogenation - Mechanistic insights and implications for hydrogen storage applications %U https://doi.org/10.1039/D3TA02205F %X The inevitable formation of passivating oxide films on the surface of the TiFe intermetallic compound limits its performance as a stationary hydrogen storage material. Extensive experimental efforts have been dedicated to the activation of TiFe, i.e. oxide layer removal prior to utilization for hydrogen storage. However, development of an efficient activation protocol necessitates a fundamental understanding of the composition and structure of the air-exposed surface and its interaction with hydrogen, which is currently absent. Therefore, in this study we explored the growth and nature of oxide films on the most exposed TiFe surface (110) in depth using static and dynamic first-principles methods. We identified the lowest energy structures for six oxygen coverages up to approximately 1.12 nm of thickness with a global optimization method and studied the temperature effects and structural evolution of the oxide phases in detail via ab initio molecular dynamics (AIMD). Based on structural similarity and coordination analysis, motifs for TiO2 and TiFeO3 as well as Ti(FeO2)x (x = 2, 3 or 5) phases were identified. On evaluating the interaction of the oxidized surface with hydrogen, a minimal energy barrier of 0.172 eV was predicted for H2 dissociation while H migration from the top of the oxidized surface to the bulk TiFe was limited by several high-lying energy barriers above 1.4 eV. Our mechanistic insights will prove themselves valuable for informed designs towards new activation methods of TiFe and related systems as hydrogen storage materials. %0 journal article %@ 0020-1669 %A Ghazanfari, M.R.,Siemensmeyer, K.,Santhosh, A.,Vrijmoed, J.C.,Tallu, M.,Dehnen, S.,Jerabek, P.,Thiele, G. %D 2023 %J Inorganic Chemistry %N 38 %P 15358–15366 %R doi:10.1021/acs.inorgchem.3c00008 %T Low-Cost, Multifunctional, and Sustainable Sodium Sulfido Ferrate(II) %U https://doi.org/10.1021/acs.inorgchem.3c00008 38 %X We introduce Na2[Fe3S4], comprising anionic layers, synthesized by a simple and straightforward solid-state method based on the fusion of binary sulfides of abundant sodium and iron. The structure crystallizes in a trigonal lattice with honeycomb cavities, as well as 25% of statistical iron vacancies in the crystal structure. The compound depicts high dielectric constants from 998 to 1850 at a frequency of 1 kHz depending on the sintering temperature, comparable with benchmark dielectric materials. According to the complex electrochemical impedance results, the compound depicts an electrical conductivity at ambient temperature. Optical investigations reveal a band gap of 1.64 eV, which is in agreement with an electronic band gap of 1.63 eV computed by density functional theory calculations. Magnetometry results reveal an antiferromagnetic behavior with a transition at 120 K. These findings introduce Na2[Fe3S4] as a sustainable multifunctional material with potential for a variety of electronic and magnetic applications. %0 journal article %@ 0364-5916 %A Alvares, E.,Jerabek, P.,Shang, Y.,Santhosh, A.,Pistidda, C.,Heo, T.,Sundman, B.,Dornheim, M. %D 2022 %J Calphad %N %P 102426 %R doi:10.1016/j.calphad.2022.102426 %T Modeling the thermodynamics of the FeTi hydrogenation under para-equilibrium: An ab-initio and experimental study %U https://doi.org/10.1016/j.calphad.2022.102426 %X FeTi-based hydrides have recently re-attracted attention as stationary hydrogen storage materials due to favorable reversibility, good sorption kinetics and relatively low costs compared to alternative intermetallic hydrides. Employing the OpenCalphad software, the thermodynamics of the (FeTi)H (0 1) system were assessed as a key basis for modeling hydrogenation of FeTi-based alloys. New thermodynamic data were acquired from our experimental pressure-composition-isotherm (PCI) curves, as well as first-principles calculations utilizing density functional theory (DFT). The thermodynamic phase models were carefully selected based on critical analysis of literature information and ab-initio investigations. Key thermodynamic properties such as dissociation pressure, formation enthalpies and phase diagrams were calculated in good agreement to our performed experiments and literature-reported data. This work provides an initial perspective, which can be extended to account for higher-order thermodynamic assessments and subsequently enables the design of novel FeTi-based hydrides. In addition, the assessed thermodynamic data can serve as key inputs for kinetic models and hydride microstructure simulations. %0 journal article %@ 0925-8388 %A Dreistadt, D.,Le, T.,Capurso, G.,Bellosta von Colbe, J.,Santhosh, A.,Pistidda, C.,Scharnagl, N.,Ovri, H.,Milanese, C.,Jerabek, P.,Klassen, T.,Jepsen, J. %D 2022 %J Journal of Alloys and Compounds %N %P 165847 %R doi:10.1016/j.jallcom.2022.165847 %T An effective activation method for industrially produced TiFeMn powder for hydrogen storage %U https://doi.org/10.1016/j.jallcom.2022.165847 %X This work proposes an effective thermal activation method with low technical effort for industrially produced titanium-iron-manganese powders (TiFeMn) for hydrogen storage. In this context, the influence of temperature and particle size of TiFeMn on the activation process is systematically studied. The results obtained from this investigation suggest that the activation of the TiFeMn material at temperatures as low as 50 °C is already possible, with a combination of “Dynamic” and “Static” routines, and that an increase to 90 °C strongly reduces the incubation time for activation, i.e. the incubation time of the sample with the two routines at 90 °C is about 0.84 h, while ∼ 277 h is required for the sample treated at 50 °C in both “Dynamic” and “Static” sequences. Selecting TiFeMn particles of larger size also leads to significant improvements in the activation performance of the investigated material. The proposed activation routine makes it possible to overcome the oxide layer existing on the compound surface, which acts as a diffusion barrier for the hydrogen atoms. This activation method induces further cracks and defects in the powder granules, generating new surfaces for hydrogen absorption with greater frequency, and thus leading to faster sorption kinetics in the subsequent absorption-desorption cycles. %0 journal article %@ 2199-160X %A Ghazanfari, M. R.,Santhosh, A.,Siemensmeyer, K.,Fuß, F.,Staab, L.,Vrijmoed, J. C.,Peters, B.,Liesegang, M.,Dehnen, S.,Oeckler, O.,Jerabek, P.,Thiele, G. %D 2022 %J Advanced Electronic Materials %N 11 %P 2200483 %R doi:10.1002/aelm.202200483 %T Large Exchange Bias, High Dielectric Constant, and Outstanding Ionic Conductivity in a Single-Phase Spin Glass %U https://doi.org/10.1002/aelm.202200483 11 %X The multigram synthesis of K2[Fe3S4] starting from K2S and FeS is presented, and its electronic and magnetic properties are investigated. The title compound obtains a defect variant of the K[Fe2Se2] structure type. Dielectric and impedance measurements indicate a dielectric constant of 1120 at 1 kHz and an outstanding ionic conductivity of 24.37 mS cm–1 at 295 K, which is in the range of the highest reported value for potential solid-state electrolytes for potassium-ion batteries. The Seebeck coefficient of the n-type conductor amounts to −60 µV K−1 at 973 K. The mismatch of the measured electrical resistivity and the predicted metal-like band structure by periodic quantum chemical calculations indicates Mott insulating behavior. Magnetometry demonstrates temperature-dependent, large exchange bias fields of 35 mT, as a consequence of the coexistence of spin glass and antiferromagnetic orderings due to the iron vacancies in the lattice. In addition, the decreasing training effects of 34% in the exchange bias are identified at temperatures lower than 20 K. These results demonstrate the critical role of iron vacancies in tuning the electronic and magnetic properties and a multifunctional material from abundant and accessible elements. %0 journal article %@ 0020-1669 %A Jerabek, P.,Santhosh, A.,Schwerdtfeger, P. %D 2022 %J Inorganic Chemistry %N 33 %P 13077-13084 %R doi:10.1021/acs.inorgchem.2c01512 %T Relativistic Effects Stabilize Unusual Gold(II) Sulfate Structure via Aurophilic Interactions %U https://doi.org/10.1021/acs.inorgchem.2c01512 33 %X The crystal structure of gold(II) sulfate is strikingly different from other coinage metal(II) sulfates. Central to the unsual AuSO4 bulk structure is the Au24+ ion with a very close Au–Au contact, which is a structural feature that does not appear in CuSO4 and AgSO4. To shed some light on this unusual behavior, we decided to investigate the relative stabilities of the coinage metal(II) sulfates utilizing periodic Density Functional Theory. By computing relative energies of the hypothetical nonrelativistic gold(II) sulfate (AuNRSO4) in different structural arrangements and performing chemical bonding analyses employing the Electron Localization Function as well as the Quantum Theory of Atoms in Molecules method, we show that the stability of the unsual AuSO4 bulk structure can be related to aurophilic interactions enabled by relativistic effects. From the relative stabilities and UV–vis spectra computed via GW methodology, we predict that AuNRSO4 would assume the structure of either copper(II) sulfate or silver(II) sulfate with almost equal likelihood and appear as bright-violet or deep-blue substances, respectively. %0 journal article %@ 1948-7185 %A Ghazanfari, M.R.,Vittadello, L.,Al-Sabbagh, D.,Santhosh, A.,Frankcom, C.,Fuß, F.,von Randow, C.A.,Siemensmeyer, K.,Vrijmoed, J.C.,Emmerling, F.,Jerabek, P.,Imlau, M.,Thiele, G. %D 2022 %J The Journal of Physical Chemistry Letters %N 30 %P 6987-6993 %R doi:10.1021/acs.jpclett.2c01689 %T Remarkable Infrared Nonlinear Optical, Dielectric, and Strong Diamagnetic Characteristics of Semiconducting K3[BiS3] %U https://doi.org/10.1021/acs.jpclett.2c01689 30 %X The ternary sulfido bismuthate K3[BiS3] is synthesized in quantitative yields. The material exhibits nonlinear optical properties with strong second harmonic generation properties at arbitrary wavelengths in the infrared spectral range and a notable laser-induced damage threshold of 5.22 GW cm–2 for pulsed laser radiation at a wavelength of 1040 nm, a pulse duration of 180 fs, and a repetition rate of 12.5 kHz. K3[BiS3] indicates semiconductivity with a direct optical band gap of 2.51 eV. Dielectric and impedance characterizations demonstrate κ values in the range of 6–13 at 1 kHz and a high electrical resistivity. A strong diamagnetic behavior with a susceptibility of −2.73 × 10–4 m3 kg–1 at room temperature is observed. These results suggest it is a promising nonlinear optical candidate for the infrared region. The synergic physical characteristics of K3[BiS3] provide insight into the correlation of optical, electrical, and magnetic properties. %0 journal article %@ 2046-2069 %A Ghazanfari, M.,Santhosh, A.,Vrijmoed, J.,Siemensmeyer, K.,Peters, B.,Dehnen, S.,Jerabek, P.,Thiele, G. %D 2022 %J RSC Advances %N 47 %P 30514-30521 %R doi:10.1039/D2RA05200H %T Large-scale synthesis of mixed valence K3[Fe2S4] with high dielectric and ferrimagnetic characteristics %U https://doi.org/10.1039/D2RA05200H 47 %X High yields of phase-pure K3[Fe2S4] are obtained using a fast, straight-forward, and efficient synthetic technique starting from the binary precursors K2S and FeS, and elemental sulphur. The compound indicates soft ferrimagnetic characteristics with magnetization of 15.23 A m2 kg−1 at 300 K due to the mixed valence of FeII/FeIII. Sintering at different temperatures allows the manipulation of the microstructure as well as the ratio of grains to grain boundaries. This results in a variation of dielectric and impedance properties. Samples sintered at 923 K demonstrate a dielectric constant (κ) of around 1750 at 1 kHz, which lies within the range of well-known high-κ dielectric materials, and an ionic conductivity of 4 × 10−2 mS cm−1 at room temperature. The compound has an optical band gap of around 2.0 eV, in agreement with tailored quantum chemical calculations. These results highlight its potential as a material comprising non-toxic and abundant elements for electronic and magnetic applications. %0 journal article %@ 2516-1083 %A Pasquini, L.,Sakaki, K.,Akiba, E.,Allendorf, M.D.,Alvares, E.,Ares, J.R.,Babai, D.,Baricco, M.,Bellosta Von Colbe, J.,Bereznitsky, M.,Buckley, C.E.,Cho, Y.W.,Cuevas, F.,De Rango, P.,Dematteis, E.M.,Denys, R.V.,Dornheim, M.,Fernández, J.F.,Hariyadi, A.,Hauback, B.C.,Heo, T.W.,Hirscher, M.,Humphries, T.D.,Huot, J.,Jacob, I.,Jensen, T.R.,Jerabek, P.,Kang, S.Y.,Keilbart, N.,Kim, H.,Latroche, M.,Leardini, F.,Li, H.,Ling, S.,Lototskyy, M.V.,Mullen, R.,Orimo, S.-I.,Paskevicius, M.,Pistidda, C.,Polanski, M.,Puszkiel, J.,Rabkin, E.,Sahlberg, M.,Sartori, S.,Santhosh, A.,Sato, T.,Shneck, R.Z.,Sørby, M.H.,Shang, Y.,Stavila, V.,Suh, J.-Y.,Suwarno, S.,Thi Thu, L.,Wan, L.F.,Webb, C.J.,Witman, M.,Wan, C.,Wood, B.C.,Yartys, V.A. %D 2022 %J Progress in Energy %N 3 %P 032007 %R doi:10.1088/2516-1083/ac7190 %T Magnesium- and intermetallic alloys-based hydrides for energy storage: modelling, synthesis and properties %U https://doi.org/10.1088/2516-1083/ac7190 3 %X Hydrides based on magnesium and intermetallic compounds provide a viable solution to the challenge of energy storage from renewable sources, thanks to their ability to absorb and desorb hydrogen in a reversible way with a proper tuning of pressure and temperature conditions. Therefore, they are expected to play an important role in the clean energy transition and in the deployment of hydrogen as an efficient energy vector. This review, by experts of Task 40 'Energy Storage and Conversion based on Hydrogen' of the Hydrogen Technology Collaboration Programme of the International Energy Agency, reports on the latest activities of the working group 'Magnesium- and Intermetallic alloys-based Hydrides for Energy Storage'. The following topics are covered by the review: multiscale modelling of hydrides and hydrogen sorption mechanisms; synthesis and processing techniques; catalysts for hydrogen sorption in Mg; Mg-based nanostructures and new compounds; hydrides based on intermetallic TiFe alloys, high entropy alloys, Laves phases, and Pd-containing alloys. Finally, an outlook is presented on current worldwide investments and future research directions for hydrogen-based energy storage. %0 journal article %@ 2515-7655 %A Pistidda, C.,Santhosh, A.,Jerabek, P.,Shang, Y.,Girella, A.,Milanese, C.,Dore, M.,Garroni, S.,Bordignon, S.,Chierotti, M.R.,Klassen, T.,Dornheim, M. %D 2021 %J JPhys Energy %N 4 %P 044001 %R doi:10.1088/2515-7655/abf81b %T Hydrogenation via a low energy mechanochemical approach: the MgB2 case %U https://doi.org/10.1088/2515-7655/abf81b 4 %X This work aims at investigating the effect that the energy transferred during particle collisions in a milling process entails on solid-gas reactions. For this purpose, the synthesis of Mg(BH4)2 from MgB2 in a pressurized hydrogen atmosphere was chosen as a model reaction. MgB2 was milled under a broad set of milling parameters (i.e. milling times and rotation regimes) and the obtained product thoroughly characterized. By proving the partial formation of Mg(BH4)2, the results of this investigation indicate that the energy transferred to the powder bed by the powder particles during milling is not negligible, in particular when the milling process is protracted for a long period.