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28 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3 [Next/Last]

Instruments / Technical Area	Publication Details	Published
B22-Multimode InfraRed imaging And Microspectroscopy	Vibrational modes and terahertz phenomena of the large-cage Zeolitic Imidazolate Framework-71 Annika F. Möslein , Jin-Chong Tan The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.2c00081 Diamond Proposal Number(s): [21472] Show Abstract ▼ Abstract: The zeolitic imidazole framework ZIF-71 has the potential to outperform other well-studied metal–organic frameworks due to its intrinsic hydrophobicity and relatively large pore size. However, a detailed description of its complex physical phenomena and structural dynamics has been lacking thus far. Herein, we report the complete assignment of the vibrational modes of ZIF-71 using high-resolution inelastic neutron scattering measurements and synchrotron radiation infrared spectroscopy, corroborated by density functional theory (DFT) calculations. With its 816 atoms per unit cell, ZIF-71 is the largest system yet for which frequency calculations have been accomplished employing the CRYSTAL17 DFT code. We discover low-energy terahertz dynamics such as gate-opening and shearing modes that are central to the functions and stability of the ZIF-71 framework structure. Nanoscale analytical methods based on atomic force microscopy (near-field infrared spectroscopy and AFM nanoindentation) further unravel the local chemical and mechanical properties of ZIF-71 single crystals.	Mar 2022
	Interface sensitivity in electron/ion yield X-ray absorption spectroscopy: The TiO2–H2O interface Matthijs A. Van Spronsen , Xiao Zhao , Maximilian Jaugstetter , Carlos Escudero , Tomas Duchon , Adrian Hunt , Iradwikanari Waluyo , Peidong Yang , Kristina Tschulik , Miquel B. Salmeron The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.1c02115 Open Access Show Abstract ▼ Abstract: To understand corrosion, energy storage, (electro)catalysis, etc., obtaining chemical information on the solid–liquid interface is crucial but remains extremely challenging. Here, X-ray absorption spectroscopy (XAS) is used to study the solid–liquid interface between TiO2 and H2O. A thin film (6.7 nm) of TiO2 is deposited on an X-ray-transparent SiNx window, acting as the working electrode in a three-electrode flow cell. The spectra are collected based on the electron emission resulting from the decay of the X-ray-induced core-hole-excited atoms, which we show is sensitive to the solid–liquid interface within a few nm. The drain currents measured at the working and counter electrodes are identical but of opposite sign. With this method, we found that the water layer next to anatase is spectroscopically similar to ice. This result highlights the potential of electron-yield XAS to obtain chemical and structural information with a high sensitivity for the species at the electrode–electrolyte interface.	Oct 2021
	Electronic structures and surface reconstructions in magnetic superconductor RbEuFe4As4 Vasily S. Stolyarov , Kirill S. Pervakov , Anna S. Astrakhantseva , Igor A. Golovchanskiy , Denis V. Vyalikh , Timur K. Kim , Sergey V. Eremeev , Vladimir A. Vlasenko , Vladimir M. Pudalov , Alexander A. Golubov , Eugene V. Chulkov , Dimitri Roditchev The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.0c02711 Show Abstract ▼ Abstract: In pnictide RbEuFe4As4, superconductivity sets in at 36 K and coexists, below 15–19 K, with the long-range magnetic ordering of Eu 4f spins. Here we report scanning tunneling experiments performed on cold-cleaved single crystals of the compound. The data revealed the coexistence of large Rb-terminated and small Eu-terminated terraces, both manifesting 1 × 2 and 2‾√×2‾√ 2 × 2 reconstructions. On 2‾√×2‾√ 2 × 2 surfaces, a hidden electronic order with a period ∼5 nm was discovered. A superconducting gap of ∼7 meV was seen to be strongly filled with quasiparticle states. The tunneling spectra compared with density functional theory calculations confirmed that flat electronic bands due to Eu 4f orbitals are situated ∼1.8 eV below the Fermi level and thus do not contribute directly to Cooper pair formation.	Oct 2020
I15-Extreme Conditions	Structural anomalies and electronic properties of an ionic liquid under nanoscale confinement Tuan Anh Pham , Riley M. Coulthard , Mirijam Zobel , Amitesh Maiti , Steven F. Buchsbaum , Colin Loeb , Patrick G. Campbell , Desiree Louise Plata , Brandon C. Wood , Francesco Fornasiero , Eric R. Meshot The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.0c01810 Diamond Proposal Number(s): [20578] Show Abstract ▼ Abstract: Ionic liquids promise far greater electrochemical performance compared to aqueous systems, yet key physicochemical properties governing their assembly at interfaces within commonly used graphitic nanopores remain poorly understood. In this work, we combine synchrotron X-ray scattering with first-principles molecular dynamics simulations to unravel key structural characteristics of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([TFSI]-) ionic liquids confined in carbon slit pores. X-ray scattering reveals selective pore filling due to size exclusion, while filled pores exhibit disruption in IL intermolecular structure, the extent of which increases for narrower slit pores. First-principles simulations corroborate this finding and quantitatively describe how perturbations in the local IL structure, particularly the hydrogen-bond network, depend strongly on the degree of confinement. Despite significant deviations in structure under confinement, electrochemical stability remains intact, which is important for energy storage based on nanoporous carbon electrodes (e.g., supercapacitors).	Jul 2020
	Competitive nucleation mechanism for CsPbBr3 perovskite nanoplatelets growth Victor M. Burlakov , Yasser Hassan , Mohsen Danaie , Henry J. Snaith , Alain Goriely The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.0c01794 Show Abstract ▼ Abstract: We analyse nucleation-controlled nanocrystal growth in a solution containing surface-binding molecular ligands, which can also nucleate compact layers on the crystal surfaces. We show that if the critical nucleus size for ligands is larger and the nucleation barrier is lower than those for crystal atoms, the ligands nucleate faster than the atoms on relatively wide crystal facets but much slower, if at all, on narrow facets. Such competitive nucleation of ligands and atoms results in ligands covering predominantly wider facets, thus excluding them from the growth process, and acts as a selection mechanism for the growth of crystals with narrower facets, the so-called nanoplatelets. The theory is confirmed by Monte Carlo simulations and validated experimentally for CsPbBr3 nanoplatelets grown from solution. We find that the anisotropic crystal growth is controlled by the growth temperature and the strength of surface bonding for the passivating molecular ligands.	Jul 2020
I09-Surface and Interface Structural Analysis	How bulk sensitive is hard X-ray photoelectron spectroscopy: accounting for the cathode-electrolyte interface when addressing oxygen redox Zachary W. Lebens-Higgins , Hyeseung Chung , Mateusz J. Zuba , Jatinkumar Rana , Yixuan Li , Nicholas V. Faenza , Nathalie Pereira , Bryan D. Mccloskey , Fanny Rodolakis , Wanli Yang , M. Stanley Whittingham , Glenn G. Amatucci , Ying Shirley Meng , Tien-Lin Lee , Louis F. J. Piper The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.0c00229 Diamond Proposal Number(s): [22250, 22148] Show Abstract ▼ Abstract: Sensitivity to the `bulk' oxygen core orbital makes hard X-ray photoelectron spectroscopy (HAXPES) an appealing technique for studying oxygen redox candidates. Various studies have reported an additional O 1s peak (530-531 eV) at high voltages, which has been considered a direct signature of the bulk oxygen redox process. Here, we find the emergence of a 530.4 eV O 1s HAXPES peak for three model cathodes, Li2MnO3, Li-rich NMC, and NMC 442, that shows no clear link to expected oxygen redox. Instead, the 530.4 eV peak for these three systems is attributed to transition metal reduction and electrolyte decomposition in the near-surface region. Claims of oxygen redox relying on photoelectron spectroscopy must explicitly account for the surface sensitivity of this technique and the extent of the cathode degradation layer.	Feb 2020
	Descriptors for electron and hole charge carriers in metal oxides Daniel W. Davies , Christopher N. Savory , Jarvist M. Frost , David O. Scanlon , Benjamin J. Morgan , Aron Walsh The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.9b03398 Show Abstract ▼ Abstract: Metal oxides can act as insulators, semiconductors, or metals depending on their chemical composition and crystal structure. Metal oxide semiconductors, which support equilibrium populations of electron and hole charge carriers, have widespread applications including batteries, solar cells, and display technologies. It is often difficult to predict in advance whether these materials will exhibit localized or delocalized charge carriers upon oxidation or reduction. We combine data from first-principles calculations of the electronic structure and dielectric response of 214 metal oxides to predict the energetic driving force for carrier localization and transport. We assess descriptors based on the carrier effective mass, static polaron binding energy, and Fröhlich electron–phonon coupling. Numerical analysis allows us to assign p- and n-type transport of a metal oxide to three classes: (i) band transport with high mobility; (ii) small polaron transport with low mobility; and (iii) intermediate behavior. The results of this classification agree with observations regarding carrier dynamics and lifetimes and are used to predict 10 candidate p-type oxides.	Jan 2020
	Highly anisotropic thermal transport in LiCoO2 Hui Yang , Jia-Yue Yang , Christopher N. Savory , Jonathan M. Skelton , Benjamin J. Morgan , David O. Scanlon , Aron Walsh The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.9b02073 Show Abstract ▼ Abstract: LiCoO2 is the prototypical cathode in lithium-ion batteries. Its crystal structure consists of Li+ and CoO2– layers that alternate along the hexagonal ⟨0001⟩ axis. It is well established that the ionic and electronic conduction are anisotropic, but little is known regarding the heat transport. We analyze the phonon dispersion and lifetimes using anharmonic lattice dynamics based on quantum-chemical force constants. Around room temperature, the thermal conductivity in the hexagonal ab plane of the layered cathode is ∼6 times higher than that along the c axis. An upper limit to the average thermal conductivity at T = 300 K of 38.5 W m–1 K–1 is set by short phonon lifetimes associated with anharmonic interactions within the octahedral face-sharing CoO2– network. Observations of conductivity <10 W m–1 K–1 can be understood by additional scattering channels including grain boundaries in polycrystalline samples. The impact on thermal processes in lithium-ion batteries is discussed.	Sep 2019
I10-Beamline for Advanced Dichroism	Monolayer modification of VTe2 and its charge density wave Paula Mariel Coelho , Kinga Lasek , Kien Nguyen Cong , Jingfeng Li , Wei Niu , Wenqing Liu , Ivan I. Oleynik , Matthias Batzill The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.9b01949 Diamond Proposal Number(s): [22532] Show Abstract ▼ Abstract: Interlayer interactions in layered transition metal dichalcogenides are known to be important for describing their electronic properties. Here, we demonstrate that the absence of interlayer coupling in monolayer VTe2 also causes their structural modification from a distorted 1T′ structure in bulk and multilayer samples to a hexagonal 1T structure in the monolayer. X-ray photoemission spectroscopy indicates that this structural transition is associated with electron transfer from the vanadium d bands to the tellurium atoms for the monolayer. This charge transfer may reduce the in-plane d orbital hybridization and thus favor the undistorted 1T structure. Phonon-dispersion calculations show that, in contrast to the 1T′ structure, the 1T structure exhibits imaginary phonon modes that lead to a charge density wave (CDW) instability, which is also observed by low-temperature scanning tunneling microscopy as a 4 × 4 periodic lattice distortion. Thus, this work demonstrates a novel CDW material, whose properties are tuned by interlayer interactions.	Aug 2019
I03-Macromolecular Crystallography I04-1-Macromolecular Crystallography (fixed wavelength)	Relative binding energies predict crystallographic binding modes of ethionamide booster lead compounds Natalie J. Tatum , Fernanda Duarte , Shina C. L. Kamerlin , Ehmke Pohl The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.9b00741 Diamond Proposal Number(s): [18598] Show Abstract ▼ Abstract: Transcriptional repressor EthR from Mycobacterium tuberculosis is a valuable target for antibiotic booster drugs. We previously reported a virtual screening campaign to identify EthR inhibitors for development. Two ligand binding orientations were often proposed, though only the top scoring pose was utilised for filtering of the large dataset. We obtained biophysically validated hits, some which yielded complex crystal structures. In some cases, the crystallised binding mode and top scoring mode agree, while for others the alternate ligand binding orientation was found. In this contribution we combine rigid docking, MD simulations and the LIE method to calculate free energies of binding and derive relative binding energies for a number of EthR inhibitors in both modes. This strategy allowed us to correctly predict the most favourable orientation. Therefore, this widely applicable approach will be suitable to triage multiple binding modes within EthR and other potential drug targets with similar characteristics.	Apr 2019

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