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DOE OSTI2020

Frequency and Time Domain Nuclear-Electronic Orbital Equation-of-Motion Coupled Cluster Methods: Combination Bands and Electronic-Protonic Double Excitations

The accurate description of excited vibronic states is important for modeling a wide range of photoinduced processes. The nuclear-electronic orbital (NEO) approach, which treats specified protons on the same level as the electrons, can describe excited electronic-protonic states. Herein the multicomponent equation-of-motion coupled cluster with singles and doubles (NEO-EOM-CCSD) method and its time-domain counterpart, TD-NEO-EOM-CCSD, are developed and implemented. The application of these methods to the HCN molecule highlights their capabilities. These methods predict qualitatively reasonable energies and intensities for a combination band corresponding to simultaneous excitation of two vibrational modes, as well as an overtone. These methods also describe states with double excitation character, such as excited electronic-protonic states corresponding to the simultaneous excitation of an electron and a proton. The ability of the NEO-EOM-CCSD method and its time-dependent counterpart to describe combination bands, overtones, and double excitations will enable a wide range of photochemical applications.

Pavosevic, Fabijan↗

DOE OSTI2022

Reversible dehydrogenation and rehydrogenation of cyclohexane and methylcyclohexane by single-site platinum catalyst

Abstract Developing highly efficient and reversible hydrogenation-dehydrogenation catalysts shows great promise for hydrogen storage technologies with highly desirable economic and ecological benefits. Herein, we show that reaction sites consisting of single Pt atoms and neighboring oxygen vacancies (V O ) can be prepared on CeO 2 (Pt 1 /CeO 2 ) with unique catalytic properties for the reversible dehydrogenation and rehydrogenation of large molecules such as cyclohexane and methylcyclohexane. Specifically, we find that the dehydrogenation rate of cyclohexane and methylcyclohexane on such sites can reach values above 32,000 mol H2 mol Pt −1 h −1 , which is 309 times higher than that of conventional supported Pt nanoparticles. Combining of DRIFTS, AP-XPS, EXAFS, and DFT calculations, we show that the Pt 1 /CeO 2 catalyst exhibits a super-synergistic effect between the catalytic Pt atom and its support, involving redox coupling between Pt and Ce ions, enabling adsorption, activation and reaction of large molecules with sufficient versatility to drive abstraction/addition of hydrogen without requiring multiple reaction sites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2026

From molecular to macroscopic: predicting liquid–liquid phase equilibria and small-angle scattering of mixtures of organic liquids from atomistic simulation using Kirkwood–Buff theory

Macroscopic phase equilibria between solutions define the functionality of many biological and industrial processes, yet they are challenging to predict due to the inherent complexity of liquids containing large molecules. This work introduces an approach for the purely predictive calculation of such phase equilibria in temperature-composition space from molecular dynamics (MD) simulations at one temperature in the single-phase region. We use an approach developed previously to obtain the entropic and enthalpic contributions to the free energy of mixing from the atomic-scale information given by MD simulations via Kirkwood–Buff theory. This allows us to accurately estimate the free energy of mixing as a function of temperature, and thus obtain liquid–liquid phase equilibria, including liquid–liquid critical points, associated binodal and spinodal lines, and composition fluctuations across a region of temperature and composition. Results for binary malonamide–alkane systems are validated by comparison to a direct experimental probe of the fluctuations: the small angle X-ray scattering intensity near zero wavenumber. The MDKB → Phase method demonstrated here provides a significant improvement in predicting liquid–liquid equilibria and free energy as a function of temperature for our systems of interest compared to conventional thermodynamic models. The accurate performance of this purely predictive approach lies in its preservation of atomistic details when determining thermodynamic properties. Furthermore, its inherent extensibility to multi-component systems will likely make the MDKB → Phase approach a valuable general tool for connecting molecular interactions to macroscopic phase equilibria and for the computational screening of materials for targeted thermodynamic behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Momentum-resolved above-threshold ionization of deuterated water

We present momentum-resolved coincidence measurements of strong-field single and double ionization of deuterated water (D 2 O) using intense few-cycle laser pulses. We measure the vector momentum of electrons and ions resulting from the laser-molecule interaction. This enables us to measure the photoelectron spectrum for electrons in coincidence with fragment ions having different momenta, which can be related to different final states of the cation and dication. The photoelectron spectra for different fragment ion momenta show striking differences, which can be interpreted in terms of the removal of electrons from different molecular orbitals, including the highest occupied molecular orbital (HOMO), as well as more deeply bound ones (e.g., HOMO-2). Here, we discuss our measurements in light of calculations which model the strong-field light matter interaction.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2020

Materials Data on ZnSiH12(OF)6 by Materials Project

Zn(H2O)6SiF6 crystallizes in the trigonal R-3 space group. The structure is zero-dimensional and consists of three SiF6 clusters and three zinc hexahydrate molecules. In each SiF6 cluster, Si4+ is bonded in an octahedral geometry to six equivalent F1- atoms. All Si–F bond lengths are 1.72 Å. F1- is bonded in a single-bond geometry to one Si4+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on TiZnH12(OF)6 by Materials Project

TiF6Zn(H2O)6 crystallizes in the trigonal R-3 space group. The structure is zero-dimensional and consists of three TiF6 clusters and three zinc hexahydrate molecules. In each TiF6 cluster, Ti4+ is bonded in an octahedral geometry to six equivalent F1- atoms. All Ti–F bond lengths are 1.89 Å. F1- is bonded in a single-bond geometry to one Ti4+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on TiZnH12(OF)6 by Materials Project

TiF6Zn(H2O)6 crystallizes in the trigonal R-3 space group. The structure is zero-dimensional and consists of three TiF6 clusters and three zinc hexahydrate molecules. In each TiF6 cluster, Ti4+ is bonded in an octahedral geometry to six equivalent F1- atoms. All Ti–F bond lengths are 1.90 Å. F1- is bonded in a single-bond geometry to one Ti4+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on ZnGe(OF)6 by Materials Project

ZnO6GeF6 is Tetraauricupride structured and crystallizes in the trigonal R-3 space group. The structure is zero-dimensional and consists of three GeF6 clusters and three zinc;hexahydrate molecules. In each GeF6 cluster, Ge is bonded in an octahedral geometry to six equivalent F atoms. All Ge–F bond lengths are 1.83 Å. F is bonded in a single-bond geometry to one Ge atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on ZnOs2(NO2)4 by Materials Project

Zn(OsO4)2(N2)2 is Iron carbide-derived structured and crystallizes in the cubic F-43m space group. The structure is zero-dimensional and consists of sixteen ammonia molecules, eight OsO4 clusters, and four zinc molecules. In each OsO4 cluster, Os5+ is bonded in a tetrahedral geometry to four equivalent O2- atoms. All Os–O bond lengths are 1.73 Å. O2- is bonded in a single-bond geometry to one Os5+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on CrN4Cl(O2F)2 by Materials Project

Cr(NF)2N2ClO4 is Iron carbide-derived structured and crystallizes in the tetragonal I4_1md space group. The structure is zero-dimensional and consists of eight ammonia molecules, four ClO4 clusters, and four Cr(NF)2 clusters. In each ClO4 cluster, there are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Cl1- atom. The O–Cl bond length is 1.49 Å. In the second O2- site, O2- is bonded in a single-bond geometry to one Cl1- atom. The O–Cl bond length is 1.43 Å. Cl1- is bonded in a tetrahedral geometry to four O2- atoms. In each Cr(NF)2 cluster, Cr3+ is bonded in a distorted see-saw-like geometry to two equivalent N2+ and two equivalent F1- atoms. Both Cr–N bond lengths are 1.91 Å. Both Cr–F bond lengths are 1.79 Å. N2+ is bonded in a single-bond geometry to one Cr3+ atom. F1- is bonded in a single-bond geometry to one Cr3+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Ru3N12(Cl4O3)2 by Materials Project

Ru(Ru(NO)2)2(N2Cl)2(N2OCl3)2 crystallizes in the orthorhombic Immm space group. The structure is one-dimensional and consists of two ruthenium molecules; four N2Cl clusters; four Ru(NO)2 clusters; and two N2OCl3 ribbons oriented in the (1, 0, 0) direction. In each N2Cl cluster, N+0.33+ is bonded in a single-bond geometry to one Cl1- atom. The N–Cl bond length is 1.57 Å. Cl1- is bonded in a distorted bent 120 degrees geometry to two equivalent N+0.33+ atoms. In each Ru(NO)2 cluster, Ru+5.33+ is bonded in a distorted tetrahedral geometry to two equivalent N+0.33+ and two equivalent O2- atoms. Both Ru–N bond lengths are 1.72 Å. Both Ru–O bond lengths are 1.82 Å. N+0.33+ is bonded in a distorted single-bond geometry to one Ru+5.33+ atom. O2- is bonded in a single-bond geometry to one Ru+5.33+ atom. In each N2OCl3 ribbon, N+0.33+ is bonded in an L-shaped geometry to two equivalent Cl1- atoms. Both N–Cl bond lengths are 1.80 Å. O2- is bonded in a distorted single-bond geometry to one O2- and four Cl1- atoms. The O–O bond length is 1.22 Å. There are two shorter (2.93 Å) and two longer (2.94 Å) O–Cl bond lengths. There are two inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a distorted L-shaped geometry to two equivalent N+0.33+ and one O2- atom. In the second Cl1- site, Cl1- is bonded in a distorted bent 150 degrees geometry to two equivalent O2- atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Bottom-up design of actinide materials from molecular clusters: Demonstration of a general-purpose simulation capability leveraging machine-learned atomic potentials

Actinide thin-film coatings such as uranium dioxide (UO 2 ) play an important role in nuclear reactors and other mission-relevant applications, but realization of their potential requires a deep fundamental understanding of the chemical vapor deposition (CVD) processes used for their growth. The slow experimental progress can be attributed, in part, to the standard safety guidelines associated with handling uranium byproducts, which are often corrosive, toxic, and radioactive. Accurate simulation techniques, when used in concert with experiment, can improve laboratory safety, material durability, and deliverable timeframes. However, state-of-the-art computational methods are either insufficiently accurate or intractably expensive. To remedy this situation, in this project we suggested a machine-learning (ML) accelerated workflow for simulating molecular clustering toward deposition. As a benchmark test case, we considered molecular clustering in steam and assessed independent components of our workflow by comparing with measured thermodynamic properties of water. After analyzing each component individually and finding no fundamental barrier to realization of the workflow, we attempted to integrate the ML component, a Sandia-developed tool called FitSNAP. As this was the first application of FitSNAP to atoms and molecules in the gas phase at Sandia, the method required more fitting data than was originally anticipated. Systematic improvements were made by including in the fit data diatomic potentials, molecular single-bond-breaking curves, and symmetry-constrained intermolecular potentials. We concluded that our strategy provides a feasible pathway toward modeling CVD and related processes, but that extensive training data must be generated before it can be of practical use.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Assembling Phenothiazine into a Porous Coordination Cage to Improve Its Photocatalytic Efficiency for Organic Transformations

Abstract Photo‐catalysis by small‐molecules is often limited by catalyst degradation and low electron‐transfer efficiency. Herein we report a stable N‐phenyl‐phenothiazine (PTH)‐derived porous coordination cage (PCC) as a highly efficient photocatalyst. By the incorporation of the photocatalytic PTH moiety into a PCC, aggregation‐induced quenching (AIQ) was shown to be reduced. An improvement in catalyst stability was discovered, ascribed to the synergistic effects of the PTH moieties. The catalyst, operating through a photolytic single‐electron transfer, was utilized for photo‐catalyzed dehalogenation and borylation. Evaluation of the catalytic mechanism in the borylation reaction showed that the improved performance results from the more efficient formation of the electron donor‐acceptor (EDA) complex with the cage. This discovery provides a potential strategy to improve the photophysical properties and stabilities of small‐molecule organic photocatalysts via supramolecular chemistry.

Chemistry↗

DOE OSTI2021

Structural Insights into the Vapochromic Behavior of Pt- and Pd-Based Compounds

Anionic complexes having vapochromic behavior are investigated: [K(H 2 O)][M(ppy)(CN) 2 ], [K(H 2 O)][M(bzq)(CN) 2 ], and [Li(H 2 O) n ][Pt(bzq)(CN) 2 ], where ppy = 2-phenylpyridinate, bzq = 7,8-benzoquinolate, and M = Pt(II) or Pd(II). These hydrated potassium/lithium salts exhibit a change in color upon being heated to 380 K, and they transform back into the original color upon absorption of water molecules from the environment. The challenging characterization of their structure in the vapochromic transition has been carried out by combining several experimental techniques, despite the availability of partially ordered and/or impure crystalline material. Room-temperature single-crystal and powder X-ray diffraction investigation revealed that [K(H 2 O)][Pt(ppy)(CN) 2 ] crystallizes in the Pbca space group and is isostructural to [K(H 2 O)][Pd(ppy)(CN) 2 ]. Variable-temperature powder X-ray diffraction allowed the color transition to be related to changes in the diffraction pattern and the decrease in sample crystallinity. Water loss, monitored by thermogravimetric analysis, occurs in two stages, well separated for potassium Pt compounds and strongly overlapped for potassium Pd compounds. Furthermore, the local structure of potassium compounds was monitored by in situ pair distribution function (PDF) measurements, which highlighted changes in the intermolecular distances due to a rearrangement of the crystal packing upon vapochromic transition.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Creating Frustrated Lewis Pairs in Defective Boron Carbon Nitride for Electrocatalytic Nitrogen Reduction to Ammonia

Abstract The electrocatalytic nitrogen reduction reaction (NRR) on metal‐free catalysts is an attractive alternative to the industrial Haber–Bosch process. However, the state‐of‐the‐art metal‐free electrocatalysts still suffer from low Faraday efficiencies and low ammonia yields. Herein, we present a molecular design strategy to develop a defective boron carbon nitride (BCN) catalyst with the abundant unsaturated B and N atoms as Lewis acid and base sites, which upgrades the catalyst from a single “Lewis acid catalysis” to “frustrated Lewis pairs (FLPs) catalysis.” 14 N 2 / 15 N 2 exchange experiments and density functional theory (DFT) calculations reveal that FLPs can adsorb an N 2 molecule to form a six‐membered ring intermediate, which enables the cleavage of N 2 via a pull–pull effect, thereby significantly reducing the energy barrier to −0.28 eV. Impressively, BCN achieves a high Faraday efficiency of 18.9 %, an ammonia yield of 20.9 μg h −1 mg −1 cat. , and long‐term durability.

Lin, Wenwen↗

DOE OSTI2022

Creating Frustrated Lewis Pairs in Defective Boron Carbon Nitride for Electrocatalytic Nitrogen Reduction to Ammonia

Lin, Wenwen↗

DOE OSTI2021

Strongly Anisotropic Thermomechanical Response to Shock Wave Loading in Oriented Samples of the Triclinic Molecular Crystal 1,3,5-Triamino-2,4,6-trinitrobenzene

All-atom molecular dynamics (MD) simulations were used to study shock wave loading in oriented single crystals of the highly anisotropic triclinic molecular crystal 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). The crystal structure consists of planar hydrogen-bonded sheets of individually planar TATB molecules that stack into graphitic-like layers. Shocks were studied for seven systematically prepared crystal orientations with limiting cases that correspond to shock propagation exactly perpendicular and exactly parallel to the graphitic-like layers. The simulations were performed for initially defect-free crystals using a reverse-ballistic configuration that generates explicit, supported shocks. Final longitudinal stress components are between ≈8.5 and ≈10.5 GPa for the 1.0 km s –1 impact speed studied. Orientation-dependent properties are reported including shock speeds, stresses, temperatures, compression ratios, and local material strain rates. Spatiotemporal maps of the temperature, stress tensor, material flow, and molecular orientations reveal complicated processes that arise for specific shock directions. Furthermore, the results indicate that TATB shock response is highly sensitive to crystal orientation, with significant qualitative differences for the time evolution of the stress tensor and temperature, elastic/inelastic compression response, defect formation and growth, critical von Mises stress, and strain rates during shock rise that span nearly an order of magnitude. A variety of inelastic deformation mechanisms are identified, ranging from crumpling of graphitic-like layers to dislocation-mediated plasticity to intense shear strain localization. To our knowledge, these are the first systematic MD simulations and analysis of explicit shock wave propagation along nontrivial crystal directions in a triclinic molecular crystal.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on H9BrO4 by Materials Project

(H2O)3H7O3H11O5BrH12O5Br2Br crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of one hydrobromic acid molecule, three water molecules, one H11O5Br cluster, one H12O5Br2 cluster, and one H7O3 cluster. In the H11O5Br cluster, there are eleven 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 distorted single-bond geometry to one O2- atom. The H–O bond length is 1.01 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the fourth 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 fifth H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.06 Å) and one longer (1.47 Å) H–O bond length. In the sixth H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.03 Å) and one longer (1.58 Å) H–O bond length. In the seventh H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.03 Å) and one longer (1.58 Å) H–O bond length. In the eighth H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.04 Å) and one longer (1.55 Å) H–O bond length. In the ninth 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 tenth H1+ site, H1+ is bonded in a single-bond geometry to one O2- and one Br1- atom. The H–O bond length is 1.01 Å. The H–Br bond length is 2.20 Å. In the eleventh H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three H1+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three H1+ atoms. In the third O2- site, O2- is bonded in a trigonal non-coplanar geometry to three H1+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to three H1+ atoms. In the fifth O2- site, O2- is bonded in a distorted water-like geometry to three H1+ atoms. Br1- is bonded in a 1-coordinate geometry to one H1+ atom. In the H12O5Br2 cluster, there are twelve inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- and one Br1- atom. The H–O bond length is 1.01 Å. The H–Br bond length is 2.12 Å. In the second H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.21 Å) and one longer (1.22 Å) H–O bond length. In the third H1+ site, H1+ is bonded in a distorted single-bond geometry to one O2- atom. The H–O bond length is 1.01 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- and one Br1- atom. The H–O bond length is 1.02 Å. The H–Br bond length is 2.12 Å. In the fifth 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 sixth 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 seventh 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 eighth 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 ninth 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 tenth H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.03 Å) and one longer (1.59 Å) H–O bond length. In the eleventh H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.08 Å) and one longer (1.38 Å) H–O bond length. In the twelfth H1+ site, H1+ is bonded in a single-bond geometry to one O2- and one Br1- atom. The H–O bond length is 1.03 Å. The H–Br bond length is 2.08 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal non-coplanar geometry to three H1+ atoms. In the second O2- site, O2- is bonded in a trigonal non-coplanar geometry to three H1+ atoms. In the third O2- site, O2- is bonded in a distorted water-like geometry to three H1+ atoms. 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 trigonal non-coplanar geometry to three H1+ atoms. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in an L-shaped geometry to two H1+ atoms. In the second Br1- site, Br1- is bonded in a distorted single-bond geometry to one H1+ atom. In the H7O3 cluster, there are seven 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 linear geometry to two O2- atoms. There is one shorter (1.08 Å) and one longer (1.41 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 0.99 Å. In the fourth 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 fifth H1+ site, H1+ is bonded in a distorted single-bond geometry to one O2- atom. The H–O bond length is 1.01 Å. In the sixth H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.05 Å) and one longer (1.50 Å) H–O bond length. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to three H1+ atoms. In the second O2- site, O2- is bonded in a trigonal non-coplanar geometry to three H1+ atoms. In the third O2- site, O2- is bonded in a trigonal non-coplanar geometry to three H1+ atoms.

36 MATERIALS SCIENCE↗