Chemically Assisted Precompression of Hydrogen Molecules in Alkaline-Earth Tetrahydrides
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
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Investigation of the role of hydrogen molecules in 1D simulation of divertor detachment
The role of neutral and charged hydrogenic molecules in detached regimes of tokamak plasmas is investigated using a simplified 1D numerical model. Using MAST Upgrade like conditions, simulations are implemented to study the rollover of target flux Γ in upstream density scan. It is found that if H 2 and H 2 + are considered in simulations a lower target temperature and a larger upstream density will be required to trigger divertor detachment under the same input power and particle flux, and the critical detachment threshold (the critical ratio of upstream static pressure to the power entering the recycling region) is found to be $^{ρ_{up}}_{ρ_{recl}}$ ~ 8.1 NMW -1 at rollover. Molecule–plasma interactions are found to be as crucial as atom–plasma interactions during divertor detachment, both of which account for the majority of plasma momentum loss in the cases studied here. Further analysis of the momentum loss decomposition shows molecule-plasma elastic collisions dominate molecule-plasma interactions, while molecular charge exchange cannot effectively reduce plasma momentum. In terms of H alpha emission, a strong rise of H alpha signal is found to be due to molecular excitation channels when the upstream density further increases after rollover.
SD1D↗
Vibrationally resolved ionization cross sections for the ground state and electronically excited states of the hydrogen molecule and its isotopomeres
An existing set of vibrationally resolved ionization cross section for the ground state and the first excited states of the hydrogen molecule, based on the Gryzinski method, is extended by cross sections for the isotopomeres of H{sub 2} (i.e. D{sub 2}, T{sub 2}, HD, HT, and DT), both for non-dissociative and dissociative ionizations. The comparison of cross sections for non-dissociative ionization of H{sub 2} with results obtained by the Molecular Convergent Close-Coupling method gives a very good agreement. The compiled tables give non-dissociative and dissociative cross sections for the ground state and the five energetically lowest electronically excited states of H{sub 2} and its isotopomeres, in each case for the first 9 vibrational levels. Data for all vibrational levels of the excited states is available online.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Avoided Level Crossing and Entangled States of Interacting Hydrogen Molecules Detected by the Quantum Superposition Microscope
Pump–probe measurements by ultrashort THz pulses can be used to excite and follow the coherence dynamics in the time domain of single hydrogen molecules (H 2 ) in the junction of a scanning tunneling microscope (STM). By tailoring the resonance frequency through the sample bias, we identified two spectral signatures of the interactions among multiple H 2 molecules. First, the avoided level crossing featured by energy gaps ranging from 20 to 80 GHz was observed because of the level repulsion between two H 2 molecules. Second, the tip can sense the signal of H 2 outside the junction through the projective measurement on the H 2 inside the junction, owing to the entangled states created through the interactions. A dipolar-type interaction was integrated into the tunneling two-level system model of H 2 , enabling accurate reproduction of the observed behaviors. Furthermore, our results obtained by the quantum superposition microscope reveal the intricate quantum mechanical interplay among H 2 molecules and additionally provide a 2D platform to investigate unresolved questions of amorphous materials.
36 MATERIALS SCIENCE↗
Temporal coherent control of resonant two-photon double ionization of the hydrogen molecule via doubly excited states
Here, we use time-delayed, counter-rotating, circularly polarized few-cycle attosecond nonoverlapping pulses to study the temporal coherent control of the resonant process of two-photon double ionization (TPDI) of hydrogen molecule via doubly excited states for pulse propagation direction along $\hat k$ either parallel or perpendicular to the molecular axis $\hat R$. For $\hat k$∥ $\hat R$ and a pulse carrier frequency of 36 eV resonantly populating the Q 2 1 Π$^+_u$ (1) doubly excited state as well as other 1 Π$^+_u$ doubly excited states, we find that the indirect ionization pathway through these doubly excited states changes the character of the kinematical vortex-shaped momentum distribution produced by the two direct ionization pathways from fourfold to twofold rotational symmetry. This result is similar to what found in TPDI of the He atom involving 1 P$^ o_ {±1}$ doubly excited states; however, angular distributions exhibiting a quantum beat effect between the ground state and a doubly excited state seen for the He atom are observed here for its molecular counterpart with an anomaly in shape and magnitude, not in frequency. The sixfold differential probability integrated over the azimuthal angle of the photoelectron pair shows that this anomaly is due to autoionization decays and quantum beats between doubly excited states. For $\hat k$⟂$\hat R$ and a broadband pulse carrier frequency of 30 eV populating the Q 1 1 Π$^+_u$(1), Q 1 1 Σ$^+_u$(1), Q 2 1 Π$^+_u$(1) , and Q 1 1 Σ$^+_u$ (2) doubly excited states, the momentum distribution is shown to exhibit dynamical electron vortices with four spiral arms, which originates from the interplay between the 1 Δ$^+_ g$ , 1 Π$^+_ g$, and 1 Σ$^+_ g$ dynamical ionization amplitudes. Our treatment within either the adiabatic-nuclei approximation or fixed-nuclei approximation shows that the latter provides a very good account for this correlated process.
74 ATOMIC AND MOLECULAR PHYSICS↗
Vibrationally resolved cross sections for proton collisions with hydrogen molecules
The semi-classical molecular convergent close-coupling approach has been applied to proton collisions with molecular hydrogen in the ground electronic and vibrational state. Cross sections for electron loss and electron capture agree well with the experimental data in the intermediate energy range where coupling between electronic reaction channels is strong and previously available calculations produce inconsistent results. Results for elastic scattering and total excitation are compared with effective one-electron coupled-channel calculations, showing that accurate target structure makes an important difference to these cross sections at intermediate energies. The excitation cross sections are calculated using both the fixed-nuclei and adiabatic-nuclei approximations for transitions from the $X^1Σ^+_{\textrm{g}}$ state to the $B^1Σ^+_{\textrm{u}}$, $B'$$^1Σ^+_{\textrm{u}}$, $B''$$^1Σ^+_{\textrm{u}}$, $EF$$^1Σ^+_{\textrm{g}}$, $GK$$^1Σ^+_{\textrm{g}}$, $H$$^1Σ^+_{\textrm{g}}$, $C$$^1Π_{\textrm{u}}$, $D$$^1Π_{\textrm{u}}$, $D'$$^1Π_{\textrm{u}}$, $I$$^1Π_{\textrm{u}}$, and $J$$^1Δ_{\textrm{g}}$ states for proton energies from to keV. We find significant differences between the present ab initio calculations and the equivelocity scaled electron-scattering data that is currently used for collisional-radiative modelling. Furthermore, the adiabatic-nuclei calculations enable us to resolve the final vibrational level after excitation, producing a complete set of cross sections for excitation of ground-state molecular hydrogen for all electronic states up to $n = 3$, where $n$ is the united-atoms-limit principle quantum number.
74 ATOMIC AND MOLECULAR PHYSICS↗
Splitting of multiple hydrogen molecules by bioinspired diniobium metal complexes: a DFT study
Splitting of molecular hydrogen (H 2 ) into bridging and terminal hydrides is a common step in transition metal chemistry. In this paper, we propose a novel organometallic platform for cleavage of multiple H 2 molecules, which combines metal centers capable of stabilizing multiple oxidation states, and ligands bearing positioned pendant basic groups. Using quantum chemical modeling, we show that low-valent, early transition metal diniobium(II) complexes with diphosphine ligands featuring pendant amines can favorably uptake up to 8 hydrogen atoms, and that the energetics are favored by the formation of intramolecular dihydrogen bonds. This result suggests new possible strategies for the development of hydrogen scavenger molecules that are able to perform reversible splitting of multiple H 2 molecules.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Benchmark calculations of electron impact electronic excitation of the hydrogen molecule
We present benchmark integrated and differential cross-sections for electron collisions with H 2 using two different theoretical approaches, namely, the R-matrix and molecular convergent close-coupling. This is similar to comparative studies conducted on electron–atom collisions for H, He and Mg. Electron impact excitation to the ${\mathrm{b}}^{3}{{\Sigma}}_{\mathrm{u}}^{+}$, ${\mathrm{a}}^{3}{{\Sigma}}_{\mathrm{g}}^{+}$, ${\mathrm{B}}^{1}{{\Sigma}}_{\mathrm{u}}^{+}$, c3Πu, ${\mathrm{E}\mathrm{F}}^{1}{{\Sigma}}_{\mathrm{g}}^{+}$, C1Πu, ${\mathrm{e}}^{3}{{\Sigma}}_{\mathrm{u}}^{+}$, ${\mathrm{h}}^{3}{{\Sigma}}_{\mathrm{g}}^{+}$, ${\mathrm{B}}^{\prime 1}{{\Sigma}}_{\mathrm{u}}^{+}$ and d3Πu excited electronic states are considered. Calculations are presented in both the fixed nuclei and adiabatic nuclei approximations, where the latter is shown only for the ${\mathrm{b}}^{3}{{\Sigma}}_{\mathrm{u}}^{+}$ state. Good agreement is found for all transitions presented. Where available, we compare with existing experimental and recommended data.
74 ATOMIC AND MOLECULAR PHYSICS↗
Validation of a collisional-radiative fluid model of hydrogenic molecules in UEDGE using the kinetic neutral code EIRENE
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Physics - Plasma physics↗
A Comparison of Electronic Structure Methods for Predicting the Hydrogenation Energies of Candidate Molecules for Hydrogen Storage
The development of novel energy materials and fuels is required to expand current available energy sources. Aiming to reach this goal, there is growing interest in using molecular hydrogen as an energy carrier due to its abundance and high energy density. Liquid organic hydrogen carriers (LOHCs) are a promising route to the large-scale storage and transport of hydrogen for use in the energy economy. The search for thermodynamically viable LOHC molecules for real world use has led to a set of constraints on the dehydrogenation enthalpy and the minimum gravimetric hydrogen capacity. These constraints allow one to formulate the search for an ideal LOHC candidate molecule as an optimization problem well suited to the strengths of machine learning and artificial intelligence computational approaches. A critical barrier to a large-scale, high-throughput screening of LOHC candidate molecules is the lack of reliable training data. Computational electronic structure methods including density functional theory, coupled cluster approximations, and diffusion Monte Carlo can be used to provide training data where experimental data are either unreliable or do not exist. In this work, we use these methods to calculate the dehydrogenation energies and enthalpies of candidate LOHC molecules.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Solution-Phase Synthesis of Platinum-Decorated Hydrogen Tungsten Bronzes for Hydrogen Atom Transfer from Oxides to Molecules
Hydrogen bronzes can be used as hydrogen donors for the broad class of reactions involving proton-coupled electron transfer (PCET). Here, in this work, we describe a method to prepare platinum-decorated hydrogen tungsten bronzes, Pt@H x WO 3 · n H 2 O with n = 0, 1, and 2, by reacting the pristine oxides at modest temperatures with a mild reducing agent, H 3 PO 2 , and H 2 PtCl 6 in an aqueous solution. We explored the tunability and kinetics of this reaction and compared it with that of archetypal gas–solid hydrogen spillover. We demonstrate that the identity of the noble metal affects the extent of bronze reduction. This suggests that the mechanism proceeds via the adsorption of a hydrogen-atom species on the noble metal. Finally, we explored the ability of the Pt-decorated hydrogen tungsten bronzes to hydrogenate a model H + /e – acceptor, 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO). The bronze phases return to their fully oxidized states along with the subsequent reduction of TEMPO to TEMPOH. Overall, this work demonstrates a solution-phase method to obtain hydrogen bronzes, which can then be used to perform hydrogen transfer reactions, providing a pathway for the use of extended transition metal oxides as stoichiometric reagents for broad classes of hydrogenation reactions.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Materials Data on CdH20C2S2(NO2)6 by Materials Project
Cd(NH)2(CNH2)2(H2)4(NO)2(H3SO4)2O2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two ac1nrvfo molecules, four hydrogen molecules, one hydrogen peroxide molecule, two methanimine molecules, two nitroxyl molecules, and one Cd(NH)2 cluster. In the Cd(NH)2 cluster, Cd2+ is bonded in a distorted linear geometry to two equivalent N+0.33- atoms. Both Cd–N bond lengths are 2.09 Å. N+0.33- is bonded in a distorted bent 120 degrees geometry to one Cd2+ and one H1+ atom. The N–H bond length is 1.04 Å. H1+ is bonded in a single-bond geometry to one N+0.33- atom.
36 MATERIALS SCIENCE↗
Materials Data on AlH18(BrO6)3 by Materials Project
(H2)2(AlH8O7Br)2(HO2)4(H2O)4H2O2(HO2Br)2(O2)2(Br)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two hydrobromic acid molecules, two hydrogen molecules, two hydrogen peroxide molecules, two hydroxyperoxide molecules, two hypobromous acid;hydrate molecules, four water molecules, two water molecules, and two AlH8O7Br clusters. In each AlH8O7Br cluster, Al3+ is bonded in a see-saw-like geometry to four O2- atoms. There are a spread of Al–O bond distances ranging from 1.74–1.99 Å. There are eight inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.66 Å) H–O bond length. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. In the eighth H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.05 Å) and one longer (1.41 Å) H–O bond length. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Br5+ atom. The O–Br bond length is 1.81 Å. In the second O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Al3+ and two H1+ atoms. In the third O2- site, O2- is bonded in a single-bond geometry to one Al3+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to three H1+ atoms. In the fifth O2- site, O2- is bonded in a distorted water-like geometry to three H1+ atoms. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one Al3+ and two H1+ atoms. In the seventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Al3+ and one Br5+ atom. The O–Br bond length is 2.07 Å. Br5+ is bonded in a distorted linear geometry to two O2- atoms.
36 MATERIALS SCIENCE↗
Materials Data on BH5C4(N2O)2 by Materials Project
(B)6(CN)4(H5(C2N)2)2(CNH2)4(CHNO2)4(N2H)4(H(CO)2)2H2 crystallizes in the orthorhombic Pnn2 space group. The structure is zero-dimensional and consists of six boron molecules; four carbamic acid molecules; four diazene molecules; two formalin formaldehyde molecules; two hydrogen molecules; four hydrogen cyanide molecules; four methylamine molecules; and two n,n'-dimethylethylenediamine molecules.
36 MATERIALS SCIENCE↗
Materials Data on KH28S4N7O16 by Materials Project
(KNH5O4)2(H2)6(NHO)2(HNO2)2(H2S)2(NH4SO)2(N2H3SO)2(NO)2(H2O)4H2O2(SO3H)2 crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of one aminohydroperoxide molecule, three hydrogen molecules, one hydrogen sulfide molecule, one hydroxylamine molecule, one hydroxylamine molecule, two water molecules, one water molecule, one KNH5O4 cluster, one N2H3SO cluster, one NH4SO cluster, and one SO3H cluster. In the KNH5O4 cluster, K1+ is bonded in a 2-coordinate geometry to one H1+ and one O2- atom. The K–H bond length is 2.41 Å. The K–O bond length is 2.64 Å. N+1.57+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.20 Å) and one longer (2.12 Å) N–O bond length. There are five inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one H1+ atom. The H–H bond length is 0.75 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the fourth H1+ site, H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.64 Å) H–O bond length. In the fifth H1+ site, H1+ is bonded in a distorted L-shaped geometry to one K1+ and one H1+ atom. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to one K1+ and two H1+ atoms. In the second O2- site, O2- is bonded in a 1-coordinate geometry to one N+1.57+, one H1+, and one O2- atom. The O–O bond length is 1.44 Å. In the third O2- site, O2- is bonded in a single-bond geometry to one N+1.57+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one H1+ and one O2- atom. In the N2H3SO cluster, there are two inequivalent N+1.57+ sites. In the first N+1.57+ site, N+1.57+ is bonded in a single-bond geometry to one S2- atom. The N–S bond length is 1.48 Å. In the second N+1.57+ site, N+1.57+ is bonded in a bent 120 degrees geometry to one H1+ and one S2- atom. The N–H bond length is 1.03 Å. The N–S bond length is 1.55 Å. There are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one S2- atom. The H–S bond length is 1.42 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one N+1.57+ atom. S2- is bonded in a tetrahedral geometry to two N+1.57+, one H1+, and one O2- atom. The S–O bond length is 1.74 Å. O2- is bonded in a distorted water-like geometry to one H1+ and one S2- atom. In the NH4SO cluster, N+1.57+ is bonded in a distorted trigonal non-coplanar geometry to two H1+ and one S2- atom. Both N–H bond lengths are 1.03 Å. The N–S bond length is 1.66 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one N+1.57+ atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one S2- atom. The H–S bond length is 1.35 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one N+1.57+ atom. S2- is bonded in a 3-coordinate geometry to one N+1.57+, one H1+, and one O2- atom. The S–O bond length is 1.65 Å. O2- is bonded in a distorted water-like geometry to one H1+ and one S2- atom. In the SO3H cluster, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. S2- is bonded in a water-like geometry to two O2- atoms. There is one shorter (1.51 Å) and one longer (1.75 Å) S–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to one S2- and one O2- atom. The O–O bond length is 1.44 Å. In the second O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the third O2- site, O2- is bonded in a single-bond geometry to one H1+ and one O2- atom.
36 MATERIALS SCIENCE↗
Materials Data on SbH5(O2F3)2 by Materials Project
H2(H3O2)2(H2O2)6(SbF4)4(F2)4 crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of four hydrofluoric acid molecules, one hydrogen molecule, two hydrogen peroxide molecules, two water molecules, one H3O2 cluster, and two SbF4 clusters. In the H3O2 cluster, there are three inequivalent H sites. In the first H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 1.61 Å. In the second H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 1.63 Å. In the third H site, H is bonded in a linear geometry to two O atoms. There is one shorter (1.26 Å) and one longer (1.30 Å) H–O bond length. There are two inequivalent O sites. In the first O site, O is bonded in a 2-coordinate geometry to two H atoms. In the second O site, O is bonded in a 1-coordinate geometry to two H atoms. In each SbF4 cluster, Sb is bonded in a 2-coordinate geometry to four F atoms. There are a spread of Sb–F bond distances ranging from 1.77–2.30 Å. There are four inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one Sb atom. In the second F site, F is bonded in a single-bond geometry to one Sb atom. In the third F site, F is bonded in a single-bond geometry to one Sb atom. In the fourth F site, F is bonded in a single-bond geometry to one Sb atom.
36 MATERIALS SCIENCE↗
Materials Data on H6SN2 by Materials Project
NH3NH2H2(NH2)2SHS1 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of four ammonia molecules, four ammonia molecules, four hydrazine;sulfane molecules, four hydrogen molecules, and four hydrogen sulfide molecules.
36 MATERIALS SCIENCE↗
Materials Data on MgH20C4Br2(N4O3)2 by Materials Project
MgC4H4(N2O3)2(NH2)4(H2)2(H2Br)2 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of eight ammonia molecules, four hydrogen molecules, four molecular hydrogen;hydrobromide molecules, and two MgC4H4(N2O3)2 clusters. In each MgC4H4(N2O3)2 cluster, Mg2+ is bonded in an octahedral geometry to six O2- atoms. There are a spread of Mg–O bond distances ranging from 1.97–2.23 Å. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a 1-coordinate geometry to two N3- and one O2- atom. Both C–N bond lengths are 1.33 Å. The C–O bond length is 1.26 Å. In the second C4+ site, C4+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.17 Å. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted single-bond geometry to one C4+ atom. In the second N3- site, N3- is bonded in a distorted single-bond geometry to one C4+ atom. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to one Mg2+ and one C4+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Mg2+ and one C4+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+ and two H1+ atoms.
36 MATERIALS SCIENCE↗