%0 journal article %@ 0364-5916 %A Hannappel, P.,Alvares, E.,Heubner, F.,Pistidda, C.,Jerabek, P.,Weißgärber, T. %D 2024 %J Calphad %N %P 102701 %R doi:10.1016/j.calphad.2024.102701 %T Thermodynamic assessment of the Ce-H and CeNi5-H system %U https://doi.org/10.1016/j.calphad.2024.102701 %X Interstitial metal hydrides (MHs) have attracted considerable attention in the field of hydrogen technology, particularly in the context of storage and compression applications. Because of their minor hysteresis effects, good cyclability, activation simplicity, and high volumetric storage density, LaNi5-based alloys are recognized as prominent candidates for hydrogen storage application. Additionally, the system’s thermodynamic and electrochemical properties can be modified to suit the requirements of a particular application by alloying specific substituents. To ascertain the thermodynamic effects of Ce addition within LaNi5, in this work the Ce-H and CeNi5-H systems have been modeled with the CALPHAD method. For this reason, in this work, two different thermodynamic models have been developed and assessed using the same pressure-composition isotherms (PCIs) datasets obtained from literature and theoretical formation energies newly calculated employing periodic density functional theory (DFT). Direct comparison of the models against each other in terms of accuracy and physical plausibility revealed that extrapolation of thermodynamic properties to data-scarce regions is more reasonable with fewer model parameters and in agreement with other similar systems within the rare-earth (RE) metal-hydride class. In addition, the CeNi5-H system was investigated by assessing the (Ce)(Ni)5 (V a,H)7 phase model, which could accurately predict hydrogen storage properties while being compatible with previously developed LaNi5-H models. Ultimately, the models developed in this study may be employed and extended to describe multi-component RE-H systems and allow for thermodynamic computations that are highly desirable for accurate predictions of hydrogen absorption/desorption properties and degradation characteristics within the (La,Ce)Ni5-H metal hydride family. %0 journal article %@ 1477-9226 %A Robb, M.G.,Bondi, L.,Rodríguez-Jiménez, S.,Garden, A.L.,Jerabek, P.,Brooker, S. %D 2024 %J Dalton Transactions %N %P 1999-2007 %R doi:10.1039/D3DT03484D %T Predictable Electronic Tuning of FeII and RuII Complexes via Choice of Azine: Correlation of Ligand pKa with Epa(MIII/II) of Complex %U https://doi.org/10.1039/D3DT03484D %X Five new mononuclear ruthenium(II) tris-ligated complexes have been synthesised, varying through the choice of azine in the family of 3-azinyl-4-(4-methylphenyl)-5-phenyl-4H-1,2,4-triazole ligands (Lazine): [Ru(Lpyridine)](PF6)2 (1), [Ru(Lpyridazine)](PF6)2 (2), [Ru(L4-pyrimidine)](PF6)2 (3), [Ru(Lpyrazine)](PF6)2 (4), [Ru(L2-pyrimidine)](PF6)2 (5). Three of them, 1·2MeCN·Et2O, 3·2MeCN·Et2O and 4·2MeCN, have been structurally characterised, confirming the presence of the meridional isomer, as was previously reported for the FeII analogues. Cyclic voltammetry studies, in dry CH3CN vs. Ag/0.01 M AgNO3, show that all five RuII complexes undergo a reversible RuIII/RuII process, with the midpoint potential (Em) increasing from 0.87 to 1.18 V as the azine is changed: pyridine < pyridazine < 2-pyrimidine < 4-pyrimidine < pyrazine. A strong inverse linear correlation (R2 = 0.98) is found between the RuIII/RuII redox potential and the calculated HOMO orbital energies, which is consistent with the expectation that it is easier to oxidise (lower Em) a metal ion with a higher HOMO orbital energy. The same trend was reported earlier for the family of analogous FeII complexes, albeit at lower values of Em in all cases. In addition, the ionisation potentials of the RuII complexes, as well as those of the other group 8 analogues (FeII and OsII), showed a linear relationship with Epa. As the MIII/II redox potentials of a family of complexes has been previously reported to correlate with ligand pKa values, a computational protocol to calculate, in silico, the pKa of the Lazine family of ligands was developed. A strong linear relationship was found between the readily calculated pKa of the Lazine ligand and the Epa of the MII complex, for all three families of complexes (R2 = 0.98). %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 %@ 1433-7851 %A Robles-Navarro, A.,Jerabek, P.,Schwerdtfeger, P. %D 2024 %J Angewandte Chemie - International Edition %N 1 %P e202313679 %R doi:10.1002/anie.202313679 %T Tipping the balance between the bcc and fcc phase within the alkali and coinage metal groups %U https://doi.org/10.1002/anie.202313679 1 %X Why the Group 1 elements crystallize in the body-centered cubic (bcc) structure, and the iso-electronic Group 11 elements in the face-centered cubic (fcc) structure, remains a mystery. Here we show that a delicate interplay between many-body effects, vibrational contributions and dispersion interactions obtained from relativistic density functional theory offers an answer to this long-standing controversy. It also sheds light on the Periodic Table of Crystal Structures. A smooth diffusionless transition through cuboidal lattices gives a detailed insight into the bcc→fcc phase transition for the Groups 1 and 11 elements. %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 %@ 1369-7021 %A Shang, Y.,Lei, Z.,Alvares, E.,Garroni, S.,Chen, T.,Dore, R.,Rustici, M.,Enzo, S.,Schökel, A.,Shi, Y.,Jerabek, P.,Lu, Z.,Klassen, T.,Pistidda, C. %D 2023 %J Materials Today %N %P 113-126 %R doi:10.1016/j.mattod.2023.06.012 %T Ultra-lightweight compositionally complex alloys with large ambient-temperature hydrogen storage capacity %U https://doi.org/10.1016/j.mattod.2023.06.012 %X In the burgeoning field of hydrogen energy, compositionally complex alloys promise unprecedented solid-state hydrogen storage applications. However, compositionally complex alloys are facing one main challenge: reducing alloy density and increasing hydrogen storage capacity. Here, we report TiMgLi-based compositionally complex alloys with ultralow alloy density and significant room-temperature hydrogen storage capacity. The record-low alloy density (2.83 g cm−3) is made possible by multi-principal-lightweight element alloying. Introducing multiple phases instead of a single phase facilitates obtaining a large hydrogen storage capacity (2.62 wt% at 50 °C under 100 bar of H2). The kinetic modeling results indicate that three-dimensional diffusion governs the hydrogenation reaction of the current compositionally complex alloys at 50 °C. The here proposed approach broadens the horizon for designing lightweight compositionally complex alloys for hydrogen storage purposes. %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 %@ 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 %@ 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 %@ 1359-7345 %A Jerabek, P.,Burrows, A.,Schwerdtfeger, P. %D 2022 %J Chemical Communications : ChemComm %N 96 %P 13369-13372 %R doi:10.1039/D2CC04928G %T Solving a problem with a single parameter: a smooth bcc to fcc phase transition for metallic lithium %U https://doi.org/10.1039/D2CC04928G 96 %X Density functional calculations for metallic lithium along a cuboidal bcc-to-fcc transformation path demonstrate that the bcc phase is quasi-degenerate with the fcc phase with a very small activiation barrier of 0.1 kJ mol−1, but becomes the dominant phase at higher temperatures in accordance with Landau theory. This resolves the long-standing controversy about the two phases for lithium. %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 %@ 0021-9606 %A Florez, E.,Smits, O.,Mewes, J.,Jerabek, P.,Schwerdtfeger, P. %D 2022 %J The Journal of Chemical Physics %N 6 %P 064304 %R doi:10.1063/5.0097642 %T From the gas phase to the solid state: The chemical bonding in the superheavy element flerovium %U https://doi.org/10.1063/5.0097642 6 %X As early as 1975, Pitzer suggested that copernicium, flerovium, and oganesson are volatile substances behaving like noble gas because of their closed-shell configurations and accompanying relativistic effects. It is, however, precarious to predict the chemical bonding and physical behavior of a solid by knowledge of its atomic or molecular properties only. Copernicium and oganesson have been analyzed very recently by our group. Both are predicted to be semiconductors and volatile substances with rather low melting and boiling points, which may justify a comparison with the noble gas elements. Here, we study closed-shell flerovium in detail to predict its solid-state properties, including the melting point, by decomposing the total energy into many-body forces derived from relativistic coupled-cluster theory and from density functional theory. The convergence of such a decomposition for flerovium is critically analyzed, and the problem of using density functional theory is highlighted. We predict that flerovium in many ways does not behave like a typical noble gas element despite its closed-shell 7𝑝21/2 configuration and resulting weak interactions. Unlike the case of noble gases, the many-body expansion in terms of the interaction energy does not converge smoothly. This makes the accurate prediction of phase transitions very difficult. Nevertheless, a first prediction by Monte Carlo simulation estimates the melting point at 284 ± 50 K. Furthermore, calculations for the electronic bandgap suggests that flerovium is a semiconductor similar to copernicium %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 %@ 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 %@ 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 %@ 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 %@ 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 %@ 0947-6539 %A Bondi, L.,Garden, A.,Totti, F.,Jerabek, P.,Brooker, S. %D 2022 %J Chemistry - A European Journal %N 22 %P e202104314 %R doi:10.1002/chem.202104314 %T Quantitative Assessment of Ligand Substituent Effects on σ- and π-Contributions to Fe−N Bonds in Spin Crossover FeII Complexes %U https://doi.org/10.1002/chem.202104314 22 %X The effect of para-substituent X on the electronic structure of sixteen tridentate 4-X-(2,6-di(pyrazol-1-yl))-pyridine (bppX) ligands and the corresponding solution spin crossover [FeII(bppX)2]2+ complexes is analysed further, to supply quantitative insights into the effect of X on the σ-donor and π-acceptor character of the Fe-NA(pyridine) bonds. EDA-NOCV on the sixteen LS complexes revealed that neither ΔEorb,σ+π (R2=0.48) nor ΔEorb,π (R2=0.31) correlated with the experimental solution T1/2 values (which are expected to reflect the ligand field imposed on the iron centre), but that ΔEorb,σ correlates well (R2=0.82) and implies that as X changes from EDG→EWG (Electron Donating to Withdrawing Group), the ligand becomes a better σ-donor. This counter-intuitive result was further probed by Mulliken analysis of the NA atomic orbitals: NA(px) involved in the Fe−N σ-bond vs. the perpendicular NA(pz) employed in the ligand aromatic π-system. As X changes EDG→EWG, the electron population on NA(pz) decreases, making it a better π-acceptor, whilst that in NA(px) increases, making it a better σ-bond donor; both increase ligand field, and T1/2 as observed. In 2016, Halcrow, Deeth and co-workers proposed an intuitively reasonable explanation of the effect of the para-X substituents on the,T1/2 values in this family of complexes, consistent with the calculated MO energy levels, that M→L π-backdonation dominates in these M−L bonds. Here the quantitative EDA-NOCV analysis of the M−L bond contributions provides a more complete, coherent and detailed picture of the relative impact of M−L σ-versus π-bonding in determining the observed T1/2, refining the earlier interpretation and revealing the importance of the σ-bonding. Furthermore, our results are in perfect agreement with the ΔE(HS-LS) vs. σp+(X) correlation reported in their work. %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. %0 journal article %@ 0947-6539 %A Bondi, L.,Garden, A.,Jerabek, P.,Totti, F.,Brooker, S. %D 2020 %J Chemistry - A European Journal %N 60 %P 13677-13685 %R doi:10.1002/chem.202002146 %T Quantitative and Chemically Intuitive Evaluation of the Nature of M−L Bonds in Paramagnetic Compounds: Application of EDA‐NOCV Theory to Spin Crossover Complexes %U https://doi.org/10.1002/chem.202002146 60 %X With the aim of improving understanding of M‐L bonds in 3d transition metal complexes, quantitative analysis by Energy Decomposition Analysis and Natural Orbital for Chemical Valence model (EDA‐NOCV) is done on octahedral spin crossover (SCO) complexes, as the transition temperature (T1/2) is sensitive to subtle changes in M‐L bonding. EDA‐NOCV analysis of Fe‐N bonds in 5 [FeII( Lazine )2(NCBH3)2], in both low spin (LS) and paramagnetic high spin (HS) states, led to (a) development of a general, widely applicable, corrected M+L6 fragmentation, tested against a family of 5 LS [FeII( Lazine )3(BF4)2], confirming that 3 Lazine are stronger ligands (ΔEorb,σ+π ≈ ‐370 kcal/mol) than 2 Lazine + 2 NCBH3 (≈ ‐335 kcal/mol), as observed; (b) analysis of Fe‐L bonding on LS → HS, reveals more ionic (ΔEelstat) and less covalent (ΔEorb) character (ΔEelstat:ΔEorb 55:45 LS → 64:36 HS), mostly due to a big drop in σ‐ (ΔEorb,σ ↓50%; ‐310 → ‐145 kcal/mol), and a drop in π‐ contributions (ΔEorb,π ↓90%; ‐30 → ‐3 kcal/mol); (c) strong correlation of observed T1/2 and ΔEorb,σ+π, for both LS and HS families (R2 =0.99 LS, R2 = 0.95 HS), but no correlation of T1/2 and ΔΔEorb,σ+π(LS‐HS) (R2 =0.11). Overall, this study has established and validated a generally applicable fragmentation and computational protocol for EDA‐NOCV M‐L bonding analysis of any diamagnetic or paramagnetic, homoleptic or heteroleptic, octahedral transition metal complex. %0 journal article %@ 2469-9950 %A Smits, O.,Jerabek, P.,Pahl, E.,Schwerdtfeger, P. %D 2020 %J Physical Review B %N 10 %P 104103 %R doi:10.1103/PhysRevB.101.104103 %T First-principles melting of krypton and xenon based on many-body relativistic coupled-cluster interaction potentials %U https://doi.org/10.1103/PhysRevB.101.104103 10 %X The solid-to-liquid phase transition for krypton and xenon is studied by means of parallel-tempering Monte Carlo simulations based on an accurate description of the atomic interactions within a many-body ansatz using relativistic coupled-cluster theory. These high-level data were subsequently fitted to computationally efficient extended Lennard-Jones and extended Axilrod-Teller-Muto types of interaction potentials. Solid-state calculations demonstrate that the many-body decomposition of the interaction energy converges well for the heavier rare gas solids, leading to solid-state properties in good agreement with experiment. The results show that it suffices to include two- and three-body interactions only for the melting simulation. The melting of the bulk is simulated for cells with cubic periodic boundary conditions, as well as within a finite cluster approach. For the latter, melting of spherical magic number clusters with increasing cluster size is studied, and the melting temperatures are obtained from extrapolation to the bulk. The calculated melting temperatures for the cluster extrapolation (the periodic approach values corrected for superheating are set in parentheses) are Tm=113.7 K (110.9 K) and Tm=160.8 K (156.1 K) for krypton and xenon, respectively. Both are in very good agreement with corresponding experimental values of 115.75 and 161.40 K. %0 journal article %@ 1433-7851 %A Smits, O.,Mewes, J.,Jerabek, P.,Schwerdtfeger, P. %D 2020 %J Angewandte Chemie - International Edition %N 52 %P 23636-23640 %R doi:10.1002/anie.202011976 %T Oganesson: A Noble Gas Element That Is Neither Noble Nor a Gas %U https://doi.org/10.1002/anie.202011976 52 %X Oganesson (Og) is the last entry into the Periodic Table completing the seventh period of elements and group 18 of the noble gases. Only three atoms of Og have been successfully produced in nuclear collision experiments, with an estimate half‐life for [[EQUATION]] of [[EQUATION]] ms. [1] With such a short lifetime, chemical and physical properties inevitably have to come from accurate relativistic quantum theory. Here, we employ two complementary computational approaches, namely parallel tempering Monte‐Carlo (PTMC) simulations and first‐principles thermodynamic integration (TI), both calibrated against a highly accurate coupled‐cluster reference to pin‐down the melting and boiling points of this super‐heavy element. In excellent agreement, these approaches show Og to be a solid at ambient conditions with a melting point of ~325 K. In contrast, calculations in the nonrelativistic limit reveal a melting point for Og of 220 K, suggesting a gaseous state as expected for a typical noble gas element. Accordingly, relativistic effects shift the solid‐to‐liquid phase transition by about 100 K. %0 journal article %@ 0947-6539 %A Buchsteiner, M.,Martinez-Rodriguez, L.,Jerabek, P.,Pozo, I.,Patzer, M.,Nöthling, N.,Lehmann, C.,Fürstner, A. %D 2020 %J Chemistry - A European Journal %N 11 %P 2509-2515 %R doi:10.1002/chem.202000081 %T Catalytic Asymmetric Fluorination of Copper Carbene Complexes: Preparative Advances and a Mechanistic Rationale %U https://doi.org/10.1002/chem.202000081 11 %X The Cu‐catalyzed reaction of substituted α‐diazoesters with fluoride gives α‐fluoroesters with ee values of up to 95 %, provided that chiral indane‐derived bis(oxazoline) ligands are used that carry bulky benzyl substituents at the bridge and moderately bulky isopropyl groups on their core. The apparently homogeneous solution of CsF in C6F6/hexafluoroisopropanol (HFIP) is the best reaction medium, but CsF in the biphasic mixture CH2Cl2/HFIP also provides good results. DFT studies suggest that fluoride initially attacks the Cu‐ rather than the C‐atom of the transient donor/acceptor carbene intermediate. This unusual step is followed by 1,2‐fluoride shift; for this migratory insertion to occur, the carbene must rotate about the Cu−C bond to ensure orbital overlap. The directionality of this rotatory movement within the C2‐symmetric binding site determines the sense of induction. This model is in excellent accord with the absolute configuration of the resulting product as determined by X‐ray diffraction using single crystals of this a priori wax‐like material grown by capillary crystallization.