Chalcogenide phase-change materials show strikingly contrasting optical and electrical properties, which has led to their extensive implementation in various memory devices. By performing spin-, ...time-, and angle-resolved photoemission spectroscopy combined with the first-principles calculation, we report the experimental results that the crystalline phase of GeSb2Te4 is topologically nontrivial in the vicinity of the Dirac semimetal phase. The resulting linearly dispersive bulk Dirac-like bands that cross the Fermi level and are thus responsible for conductivity in the stable crystalline phase of GeSb2Te4 can be viewed as a 3D analogue of graphene. Our finding provides us with the possibility of realizing inertia-free Dirac currents in phase-change materials.
This computational work is devoted to the investigation (MP2/def2-TZVP) of the geometry and IR parameters of arsinic acid H
AsOOH and its hydrogen-bonded complexes under vacuum and in media with ...different polarity. The medium effects were accounted for in two ways: (1) implicitly, using the IEFPCM model, varying the dielectric permittivity (
) and (2) explicitly, by considering hydrogen-bonded complexes of H
As(O)OH with various hydrogen bond donors (41 complexes) or acceptors (38 complexes), imitating a gradual transition to the As(OH)
or AsO
moiety, respectively. It was shown that the transition from vacuum to a medium with
> 1 causes the As(O)OH fragment to lose its flatness. The solvent polar medium introduces significant changes in the geometry and IR spectral parameters of hydrogen-bonded complexes too: as the polarity of a medium increases, weak hydrogen bonds become weaker, and strong and medium hydrogen bonds become stronger; in the case of a complex with two hydrogen bonds cooperativity effects are observed. In almost all cases the driving force of these changes appears to be preferential solvation of charge-separated structures. In the limiting case of complete deprotonation (or conversely complete protonation) the vibrational frequencies of ν
and
turn into
(asym) and
(sym), respectively. In the intermediate cases the distance between ν
and
is sensitive to both implicit solvation and explicit solvation and the systematic changes of this distance can be used for estimation of the degree of proton transfer within the hydrogen bond.
This computational work is devoted to the investigation (MP2/def2-TZVP) of the geometry and IR parameters of arsinic acid H2AsOOH and its hydrogen-bonded complexes under vacuum and in media with ...different polarity. The medium effects were accounted for in two ways: (1) implicitly, using the IEFPCM model, varying the dielectric permittivity (ϵ) and (2) explicitly, by considering hydrogen-bonded complexes of H2As(O)OH with various hydrogen bond donors (41 complexes) or acceptors (38 complexes), imitating a gradual transition to the As(OH)2+ or AsO2− moiety, respectively. It was shown that the transition from vacuum to a medium with ϵ > 1 causes the As(O)OH fragment to lose its flatness. The solvent polar medium introduces significant changes in the geometry and IR spectral parameters of hydrogen-bonded complexes too: as the polarity of a medium increases, weak hydrogen bonds become weaker, and strong and medium hydrogen bonds become stronger; in the case of a complex with two hydrogen bonds cooperativity effects are observed. In almost all cases the driving force of these changes appears to be preferential solvation of charge-separated structures. In the limiting case of complete deprotonation (or conversely complete protonation) the vibrational frequencies of νAs=O and νAs–O turn into νAs–O(asym) and νAs–O(sym), respectively. In the intermediate cases the distance between νAs=O and νAs–O is sensitive to both implicit solvation and explicit solvation and the systematic changes of this distance can be used for estimation of the degree of proton transfer within the hydrogen bond.
Triphenylpnictogens were oxidized to access diphenylpnictioginic acids Ph
XOOH (X = P, As, Sb, Bi). It was shown that oxidation with chloramine-T does not lead to the cleavage of a C-pnictogen bond. ...The preliminary reductive cleavage with sodium in liquid ammonia followed by the oxidation with hydrogen peroxide was successfully utilised for the synthesis of diphenylphosphinic and diphenylarsinic acids. It was shown that in solid state (by means of XRD), all diphenylpnictoginic acids form polymeric chains. Diphenylbismuthinic and diphenylantimonic acids form polymeric covalent adducts, while diphenylphosphinic and diphenylarsinic chains are associated through hydrogen bonding. Unlike diphenylphosphinic acid, diphenilarsinic acid forms two polymorphs of hydrogen-bonded infinite chains. In solution in a polar aprotic solvent diphenylarsinic acid, similarly to dimethylarsinic, forms hydrogen-bonded cyclic dimers together with a small amount of cyclic trimers.
During the interaction of aqueous-ethanol or ethanol solutions AgNO3, HAuCl4, and CuCl2, as well as aqueous suspensions of slightly soluble copper(II) salts Cu(C6H4NO2)2·H2O, Cu(C7H5O2)2∙3H2O, and ...CuC7H4O3∙H2O with the ethanol solution of clotrimazole at pH of ~(5.0–5.5), the Ag(C22H17ClN2)2NO3·2H2O, Au(C22H17ClN2)Cl3, Cu(C22H17ClN2)2Cl2·5H2O, Cu(C22H17ClN2)4(C6H4NO2)2, Cu(C22H17ClN2)4(C7H5O2)2, and Cu(C22H17ClN2)3(C7H4O3)·2H2O compounds are synthesised. They are characterised by elemental, thermal, thermogravimetric, and IR spectroscopic methods of analysis. The Ag(C22H17ClN2)2NO3·2H2O complex was shown to have a higher antimycotic activity against Saccharomyces cerevisiae fungi than that of AgNO3 and C22H17ClN2. Cocrystals/salts of the composition C22H17ClN2·C6H5NO2, C22H17ClN2·C7H6O2, 2C22H17ClN2·C7H6O3, and 2C22H17ClN2·C19H19O6N7·H2O are obtained from aqueous and aqueous ethanol suspensions containing nicotinic, benzoic, salicylic, and folic acids and clotrimazole (pH is 4.5–6.0). These cocrystals and salts were studied usin thermogravimetric, IR-spectroscopic methods. Diffraction patterns of the powders were obtained. The influence of the difference in the pKa components on the ability to form cocrystals/salts was assessed.
MXenes are versatile 2D materials demonstrating outstanding electrochemical and physical properties, but their practical use is limited, because of fast degradation in an aqueous environment. To ...prevent the degradation of MXenes, it is essential to understand the atomistic details of the reaction and to identify active sites. In this letter, we provided a computational analysis of the degradation processes at the interface between MXene basal planes and water using enhanced sampling ab initio molecular dynamics simulations and symbolic regression analysis. Our results indicate that the reactivity of Ti sites toward the water attack reaction depends on both local coordination and chemical composition of the MXene surfaces. Decreasing the work function of the Ti3C2 T x surfaces and avoiding Ti sites that are loosely anchored to the subsurface (e.g., O-coordinated) can improve surface stability. The developed computational framework can be further used to investigate other possible culprits of the degradation reaction, including the role of defects and edges.
The control of hydrogen concentration and diffusion in metal alloys is critical for advancing clean energy technologies. A quantitative understanding of the composition-property relationship can ...accelerate the design of hydrogen storage materials, structural hydrogen-resistant alloys, and materials for energy-efficient nanoelectronics. In this work, we employed Density Functional Theory simulations to investigate the energy landscape of hydrogen absorption and mobility for a wide spectrum of high-entropy alloys and intermetallic compounds. Our study sheds light on the origin of hydrogen stability also providing quantitative guidance for compositional considerations and the design of technologically useful materials. The developed analytical model uses physically intuitive metrics characterizing the local environment, such as electronic structure features, volume of interstitial voids, and lattice vibrational modes, to predict the energy landscape of hydrogen in metal alloys based on simple calculations of bulk properties. The developed model exhibits remarkable accuracy in predicting hydrogen binding energy, achieving a low mean absolute error of less than 0.1 eV. Utilizing this model, we successfully predicted hydrogen absorption energies and migration barriers demonstrating that these quantities are linearly correlated, akin to the Brønsted-Evans-Polanyi principle. In addition, our study revealed that a similar list of material features can be employed to predict zero-point energy contribution associated with hydrogen vibrational motion.
This study identified a small set of electronic, structural, and dynamic descriptors that can be used to predict energy landscapes of hydrogen absorption and diffusion across various compositions of complex metal alloys.
This computational work is devoted to the investigation (MP2/def2-TZVP) of the geometry and IR parameters of arsinic acid H
2
AsOOH and its hydrogen-bonded complexes under vacuum and in media with ...different polarity. The medium effects were accounted for in two ways: (1) implicitly, using the IEFPCM model, varying the dielectric permittivity (
) and (2) explicitly, by considering hydrogen-bonded complexes of H
2
As(O)OH with various hydrogen bond donors (41 complexes) or acceptors (38 complexes), imitating a gradual transition to the As(OH)
2
+
or AsO
2
−
moiety, respectively. It was shown that the transition from vacuum to a medium with
> 1 causes the As(O)OH fragment to lose its flatness. The solvent polar medium introduces significant changes in the geometry and IR spectral parameters of hydrogen-bonded complexes too: as the polarity of a medium increases, weak hydrogen bonds become weaker, and strong and medium hydrogen bonds become stronger; in the case of a complex with two hydrogen bonds cooperativity effects are observed. In almost all cases the driving force of these changes appears to be preferential solvation of charge-separated structures. In the limiting case of complete deprotonation (or conversely complete protonation) the vibrational frequencies of ν
As&z.dbd;O
and
ν
As-O
turn into
ν
As-O
(asym) and
ν
As-O
(sym), respectively. In the intermediate cases the distance between ν
As&z.dbd;O
and
ν
As-O
is sensitive to both implicit solvation and explicit solvation and the systematic changes of this distance can be used for estimation of the degree of proton transfer within the hydrogen bond.
Arsinic acid H
2
As(O)OH can be strongly bound by various hydrogen bond donors and acceptors. The strength of this bond can be estimated using the distance between
ν
As=O
and
ν
As-O
bands in its IR spectra.
Incorporating hydrogen into complex oxides holds promise for discovering exotic phenomena and novel functionalities by promoting couplings between ion and lattice/charge/spin/orbital degrees of ...freedom. Here, electrolyte gating‐driven hydrogenation is investigated in epitaxial brownmillerite SrFeO2.5 thin films in which the hydrogenation‐induced lattice distortion is qualitatively different from its counterpart SrCoO2.5. The achievable lattice expansion in hydrogenated SrFeO2.5 is weaker than in SrCoO2.5 and primarily occurs along the normal of the stacked octahedral FeO6 and tetrahedral FeO4 layers. Upon the substitution of Fe with Co, the lattice expansion monotonically increases with increase of Co/Fe ratio, implying an intrinsic difference in accommodating hydrogen between Fe‐ and Co‐based brownmillerites. Moreover, a net magnetic moment in hydrogenated SrFeO2.5 films is observed above room temperature, which gradually weakens with the increase of Co substitution, suggesting a stronger canted magnetism in Fe‐based hydrogenated brownmillerites. This work clarifies the electrolyte gating‐driven hydrogenation mechanisms in brownmillerite SrFeO2.5 epitaxial thin films and those with Co substitution, particularly the deterministic role of Co/Fe ratio in the evolution of structure and properties upon hydrogenation.
The hydrogenation induced by ionic liquid gating in epitaxial SrFeO2.5 demonstrates distinctive dependences of structural evolutions on crystallographic orientations and Co substitutions, and promotes a ferromagnetic order above room temperature in SrFeO2.5, which gradually weakens with Co substitution increases. This work reveals the mechanisms for hydrogenation in BM‐SFO, and provides insight into optimizing the hydrogenation‐related functionalities by designing the Co/Fe compositions.
Triphenylpnictogens were oxidized to access diphenylpnictioginic acids Ph
2
XOOH (X = P, As, Sb, Bi). It was shown that oxidation with chloramine-T does not lead to the cleavage of a C-pnictogen ...bond. The preliminary reductive cleavage with sodium in liquid ammonia followed by the oxidation with hydrogen peroxide was successfully utilised for the synthesis of diphenylphosphinic and diphenylarsinic acids. It was shown that in solid state (by means of XRD), all diphenylpnictoginic acids form polymeric chains. Diphenylbismuthinic and diphenylantimonic acids form polymeric covalent adducts, while diphenylphosphinic and diphenylarsinic chains are associated through hydrogen bonding. Unlike diphenylphosphinic acid, diphenilarsinic acid forms two polymorphs of hydrogen-bonded infinite chains. In solution in a polar aprotic solvent diphenylarsinic acid, similarly to dimethylarsinic, forms hydrogen-bonded cyclic dimers together with a small amount of cyclic trimers.
Self-association of diphenylpnictoginic acids Ph
2
XOOH was studied in solution and solid state. Diphenylbismuthinic and diphenylantimonic acids form polymeric covalent adducts, while diphenylphosphinic and diphenylarsinic form H-bonded associates.
