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Neutron Vibrational Spectroscopy

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Neutron Vibrational Spectroscopy Neutron Vibrational Spectroscopy A.J. (Timmy) Ramirez-Cuesta Luke L. Daemen Yongqiang Cheng Spallation Neutron Source Oak Ridge National Laboratory ORNL is managed by UT-Battelle for the US Department of Energy The S(Q,w) Map w=0 Elastic Scattering Diffraction Structural Information 2 "Let there be light" 3 4 How to measure INS (1) Direct Geometry Instrumentation 4000 3500 Direct geometry instruments 3000 ) 1 - m measure Q trajectory is c ( 2500 r e f determined by the angle s n 2000 a r t and energy transfer. y g r 1500 e n Examples: ARCS, CNCS, E HYSPEC, SEQUIOA 1000 500 0 0 10 20 30 Momentum transfer (A-1) ) . U . A ( y t i s n e L t 2 n I Incident neutron beam is 0 10 20 30 40 50 60 70 Energy (meV) s monochromatic t n u o c determining the incident n o r t u Distance energy E1. e N That determines T1. We L1 12000 13000 14000 15000 16000 measure the ToF and we ToF (ms) can work out T2. Resolution is almost constant in units of Ei time 5 VISION: a high throughput spectrometer for neutron vibrational spectroscopy Yongqiang Cheng, Luke Daemen, A.J. (Timmy) Ramirez-Cuesta Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37931 USA VISION offers users a variety of sample environments How to measure INS (2) Polybenzene nanothreads synthesized at high pressure: single nanothreads VISION is best thought of as and experimental/computational capabilities: the neutron analogue of a Structural inference through modeling of vibrational spectra Indirect Geometry Instrumentation Raman spectrometer. It is optimized to characterize molecular vibrations in a wide Benzene samples were compressed to 20 GPa at room temperature, 4000 range of crystalline and maintained at this pressure for one hour, and slowly released to ambient y 3500 t i disordered materials over a s pressure at an average rate of 2 GPa /hr to recover a solid white product. L n 2 e t broad energy range (1 meV 3000 n I ) 1 - to >500 meV), while m c ( 2500 supercomputers and r simultaneously recording e f s 0 50 100 150 200 250 300 350 computer clusters with n 2000 a structural changes using r t s Energy transfer (meV) DFT and past-DFT codes t y n 40 g diffraction detectors in the u r 1500 e o c n 3 mg sample synthesized on SNAP in diamond E backscattering position and n 1000 o r t 20 anvil cells and measured on VISION. u at 90°. ortho/para H e 2 500 N ✔ converter 0 Comparison of the experimental data from 0 5000 10000 15000 20000 25000 30000 L1 0 10 20 30 VISION and a series of DFT calculations of -1 ToF (ms) JANIS closed-cycle Momentum transfer (A ) 3 refrigerator (5-600K) hypothetical structures that contain sp carbon and the correct stoichiometry (C:H ratio 1:1) Resolution is almost constant in units of Δω/ω~1.5% allows us to determine which structure Proposed mechanism of polymerization Distance corresponds to the measured spectra. (zipper structure) ✔ Figures on the far left show the superposition of Computer modeling is vital to understand the measured spectrum of polybenzene with the spectra. The calculations shown here time calculated INS spectra of the structures took up to 36 hours using 1024 cores with 3 DOI: 10.10 38/ NMAT4CASTE088 P/Materials Studio Incident neutron beam is white. We (containing sp carbon) shown in the right column: SUPPLEMENTARY INFORMATION ✔ top =graphane, middle = tubular structure (highly fix the energy of the scattered in situ electrochemical impedance symmetric) and bottom = zipper structure. The neutrons using a analyzer and filter spectroscopy (EIS) zipper structure provides the better agreement device. between calculation and experiment. That fixes T2. We measure the ToF and we can work out T1. Gas handling panel for gas dosing, mixing, flow, adsorption 6 (vacuum to 200 bar) VISION is an inverted geometry instrument that offers enhanced performance by coupling a white beam of incident neutrons with two banks of seven analyzer modules (double-focusing crystal arrays). This Pressure cells (piston, gas, DAC) arrangement leads to improved signal-to-background ratio, and the overall Collaboration with Malcolm Guthrie, Supplementary FigurJohe 9: Nnan Baothrddeadin forg,m eVd biny cCreycloaspidditi on and intramolecular count rate in the inelastic signal is more than two orders of magnitude reaction. Top: A reaction mechanism that forms a sp3 nanothread from benzene molecules The VISION team is always interested in developing and Original publication on carbon greater than that of similar spectrometers currently available. arranged in the benzenena II nocrysthretal. Benadzenes: m Naolectureules ar eMateria oriented in ls,a sl ipp14ed, s43tack along both adding new sample environment capabilities in collaboration the a and b axes of the benzene II crystal structure. An a axis stacking extracted from this crystal (2014) with users. structure is shown in the leftmost column. A series of [4 +2 ] cycloaddition reactions can form a benzene polymer (second and third columns). Aligned olefin functions are then well oriented for a zipper cascade30 to give a fully sp3 hybridized nanothread (fourth column). The cycloaddition and zipper reactions both have negative activation volumes and would thus be promoted under high pressure. The zipper reaction is very exothermic; the slow decompression employed in our experiments may aid in controlling this reaction. Tight binding relaxation of the [4 +2 ] cycloaddition reaction product spontaneously forms the fully sp3 thread in view of its Crystallization of amorphous calcium carbonate Nitrogen adsorption in ZIF-8 metal-organic framework Order-disorder transition in methylammoconsiderable thermniumodynamic st ableaility. Thids st iodidructure can inteerco nvert to the (3,0) and polymer I structures discussed in the main text by Stone-Wales transformation: all three structures should be considered members of a single structural family, since current scattering data does not provide a firm basis to distinguish between them. Although benzene dimers are prone to • Neutron vibrational spectrum cycloreversion, benzene oligomers several repeat units long can be formed at hundreds of MPa 12 – Simiprlaressu tores IR in theand liqu Ramid statean,31. H butigh p rnoessu sreel solecid-tistonate rulespolymer ization appears to facilitate • Amorphous Calcium Carbonate CH NH librations 10 3 3 MAPbI 3 – MA fvoribrationmation of sm domiuch lonnateger str ucduetures to. B lotargetom: Sitncrucoherentturally relax neutroned nanothr ead formed by this (ACC) plays an important role 8 DFT NH torsion 6 3 Fundamentals scattering cross-section for H in biomineralization H2O LIBRATIONS 4 1st overtones • Density functional theory 2 NATURE MATERIALS | www.nature.com/ naturematerials 23 0 – Use structural data as input to calculate phonons/vibrations • ACC is also of great interest 60 • Vibrational eigenvectors for CO2 sequestration 50 40 MAPbI • Use as input to calculate neutron spectrum y t 3 i 30 s Neutron • Provides vibrational mode assignments n e 20 t T = 5 K n • Different types/structures of ACC I 10 • I. Milas and Y.Q. Cheng (ORNL) 0 • Measurements of vibrations and phonons are important for with varying amounts of water and 0 500 1000 1500 2000 -1 understanding local order Energy (cm ) – Electron-phonon coupling (charge transport) – Thermal conductivity (heat capacity) • What is the nature of the Comparison of neutron and DFT crystallization phase transition, spectra provides a demanding test which is accompanied by the of accuracy of DFT calculation photovoltaic applications expulsion of water? • Well defined vibrational modes at T = 5 K • Modes broaden significantly • Simultaneous inelastic and with temperature diffraction measurements on – Increasing Debye-Waller VISION at increasing temperatures factor show progressive water loss • Above the MA order-disorder without crystallization transition at T = 160 K the modes are replaced by • Onset of crystallization quasielastic scattering around 530 K is accompanied by water expulsion, but takes 40 mins to complete. 327 K Endothermic dehydration of hydrous ACC starts at ~100°C, and is followed by a sharp exothermic crystallization (at ~530K) of the Cubic (a = b = c) Tetragonal (a = b c) anhydrous ACC to calcite. Schematic representation of 2ac x 2ac x 2cc the free energy profile for the nonclassical formation of CaCO3 According to the corresponding from ion pairs in solution. Here the two lines for ACC represent ZIF-8 = Zn(mIM) = zinc (methyl imidazole) temperature powder diffraction the bounds of a distribution of 2 2 measurements on VISION/NOMAD, possible curves depending on the bound H2O content (Raiteri P. anhydrous ACC persists up and Gale J.D. J. Am. Chem. Soc. • Structures determined by 2010, 132, 17623. N2 adsorbed in the ZIF-8 framework breaks the synchronicity to 530K before crystallization to calcite. of the methyl torsions in the lattice. This effects translates neutron powder into a change in local structure ("gate opening" effect) diffraction at Spallation NOMAD data Orthorhombic (a b c) Neutron Source (ORNL) 2ac x 2ac x 2cc MAPbI3: Two Structural Phase Transitions Collaboration with K.Page, H-W Wang, A. Stack, ORNL Collaboration with Joaquin Silvestre-Albero, Univeristy of Alicante, Spain Collaboration with M. Crawford, DuPont Effect of the Instrument Geometry k’ Q 2휃 k k’ Q 2휃 7 k SNS Instrument Suite 8 analyzers VISION neutron beam diffraction detectors inelastic detectors • Vibrational spectroscopy with neutrons • Beam line started commissioning 2 years ago • Multifunctional beam line: simultaneous spectroscopy and diffraction • Dynamic range: 0-1000 meV; resolution: < 1.5% • Diffraction: 1.5 - 30 A-1 • Temperature range: 5-700K • Sample environment: high pressure, electric field, gas loading, ... • Great sensitivity to hydrogen, no selection rules, penetration through matter, ... 9 The VISION instrument • White incident beam, fixed final energy (indirect geometry) • High flux (~5x107 neutrons/cm2/s) and double-focusing • Broadband (-2 to 1000 meV at 30Hz, 5 to 500 meV at 60 Hz) • Constant dE/E throughout the spectrum (~1.5%) • Elastic line HMFW ~150 μs • Backward and 90° diffraction banks 10 Sample environment JANIS closed-cycle Pressure cells refrigerator (5-700K) (piston, gas, Gas handling panel for diamond anvil).
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