Orthogonal strains and onset of plasticity in shocked LiF crystals

Whitlock, R. R.; Wark, J. S.

doi:10.1103/physrevb.52.8

Cited by 28 publications

(18 citation statements)

References 14 publications

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“…1 Since the pioneering efforts of Johnson et al [2][3][4] in the early 1970s, different attempts have been reported in the literature [5][6][7][8][9][10][11][12] including the recent work by Wark and co-workers using laser-induced shocks. [10][11][12] A careful examination of the reported attempts revealed that various limitations in the existing studies ͑less than optimal x-ray quality, spatial and temporal nonuniformites of shock loading, use of free surface measurements, etc.͒ have precluded quantitative measurements and analysis.…”

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confidence: 99%

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Real-time x-ray diffraction to examine elastic–plastic deformation in shocked lithium fluoride crystals

Rigg

Gupta

1998

Applied Physics Letters

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Pressure effect and Mn doping in NaxCoO2 J. Appl. Phys. 112, 053503 (2012) Raman study of the Verwey transition in magnetite at high-pressure and low-temperature: Effect of Al doping J. Appl. Phys. 112, 043510 (2012) Dielectric spectroscopy and ultrasonic study of propylene carbonate under ultra-high pressures J. Chem. Phys. 137, 084502 (2012) Structural changes of filled ice Ic hydrogen hydrate under low temperatures and high pressures from 5 to 50 GPa J. Chem. Phys. 137, 074505 (2012) Additional information on Appl. Phys. Lett.

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“…In contrast, large shock compression along the ͓100͔ direction reportedly results in an isotropic compression of the unit cell. 3,8,12 The experimental configuration for obtaining x-ray diffraction data from shocked single crystals is shown schematically in Fig. 1.…”

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Real-time x-ray diffraction to examine elastic–plastic deformation in shocked lithium fluoride crystals

Rigg

Gupta

1998

Applied Physics Letters

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“…Indeed, such time-resolved X-ray diffraction (TXRD) methods have been used extensively to study shock phenomena for several decades [12][13][14][15][16][17][18][19][20] , with several notable successes, including the direct observation of the a À e transition in shock-compressed iron 6,21 . Some progress in understanding rapid shock-induced plasticity has been made: diffraction of monochromatic X-rays from planes parallel and perpendicular to the shock propagation direction has directly detected elastic strain in both directions (which gives a measure of plastic strain, as the total strain (elastic plus plastic) perpendicular to the shock propagation direction in a uniaxially strained material is zero) 16,[22][23][24][25] . Furthermore, broadening of the diffraction peaks observed in both shocked copper 25 , aluminium 26 and LiF 27 are consistent with large defect densities and/or lattice rotations.…”

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Nanosecond white-light Laue diffraction measurements of dislocation microstructure in shock-compressed single-crystal copper

et al. 2012

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Under uniaxial high-stress shock compression it is believed that crystalline materials undergo complex, rapid, micro-structural changes to relieve the large applied shear stresses. Diagnosing the underlying mechanisms involved remains a significant challenge in the field of shock physics, and is critical for furthering our understanding of the fundamental lattice-level physics, and for the validation of multi-scale models of shock compression. Here we employ white-light X-ray Laue diffraction on a nanosecond timescale to make the first in situ observations of the stress relaxation mechanism in a laser-shocked crystal. The measurements were made on single-crystal copper, shocked along the [001] axis to peak stresses of order 50 GPa. The results demonstrate the presence of stress-dependent lattice rotations along specific crystallographic directions. The orientation of the rotations suggests that there is double slip on conjugate systems. In this model, the rotation magnitudes are consistent with defect densities of order 10 12 cm À 2 .

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“…2 Provided one succeeds in generating short bursts of electrons or X-rays, both electron diffraction and X-ray diffraction [38][39][40][41][42][43][44][45][46][47][48][49] can be adapted to the time domain. Indeed, developments of the recent past have shown that it is possible to generate pulses of even subpicosecond duration of both X-rays 49-51 and electrons.…”

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Ultrafast Diffraction Imaging of the Electrocyclic Ring-Opening Reaction of 1,3-Cyclohexadiene

2001

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Changes in electron diffraction patterns are observed on ultrashort time scales upon irradiation of 1,3-cyclohexadiene with femtosecond laser pulses. 1,3-Cyclohexadiene is known to experience a ring opening reaction to hexatriene upon excitation to the 1 B 2 electronic state. Internal conversion brings the molecule to a saddle point, from where one pathway leads back to cyclohexadiene, while another path generates 1,3,5-hexatriene in one of its isomeric forms. Structural observations are made at picosecond time delays using an ultrashort electron pulse that is diffracted off the nascent product molecules. The diffraction images illustrate that structural observations of prototypical organic reactions can be made in real time, opening a new methodology to study chemical reaction dynamics.Molecular spectroscopy with femtosecond or picosecond time resolution has become tremendously successful in exploring energy relaxation processes and chemical reactions in real time. It is now possible to obtain spectra of molecules just as they cross a transition state during a chemical reaction. 1 Such spectroscopic studies have led to enormous insights about the flow of energy within and between molecules, allowing detailed inferences about the mechanisms of the reactions.Nonetheless, time-resolved spectroscopy is burdened by fundamental constraints. Most mechanistic chemistry is based on structural models, whereas spectroscopy reveals energy levels. Synthetic chemists describe reactions as transformations of molecular structures, with reaction channels that are determined by spatial distributions of functional groups, steric hindrances, or spatial electrostatic charge distributions. In contrast, spectroscopy can measure only energy levels and populations of molecules in energy levels. Thus, time-resolved spectroscopy, however useful, shows only the time dependence of energy level populations.Energy levels and structures are of course connected via potential energy surfaces and quantum mechanics. However, this link is conceptually difficult, and tremendous computational resources must applied to understand even simple chemical reactions from a quantum mechanical perspective. It therefore has been a long-standing goal of experimental physical chemists to observe time-dependent structures of molecules during chemical reactions. Such structural observations carry the promise of a much more direct connection to mechanistic organic chemistry. We report here the investigation of a prototypical organic reaction by time-resolved electron diffraction.The concept of probing time dependent molecular structures by diffraction has been well documented. 2 Provided one succeeds in generating short bursts of electrons or X-rays, both electron diffraction 3-37 and X-ray diffraction 38-49 can be adapted to the time domain. Indeed, developments of the recent past have shown that it is possible to generate pulses of even subpicosecond duration of both X-rays 49-51 and electrons. 29 In time-domain diffraction experiments a short laser pulse initia...

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Orthogonal strains and onset of plasticity in shocked LiF crystals

Cited by 28 publications

References 14 publications

Real-time x-ray diffraction to examine elastic–plastic deformation in shocked lithium fluoride crystals

Real-time x-ray diffraction to examine elastic–plastic deformation in shocked lithium fluoride crystals

Nanosecond white-light Laue diffraction measurements of dislocation microstructure in shock-compressed single-crystal copper

Ultrafast Diffraction Imaging of the Electrocyclic Ring-Opening Reaction of 1,3-Cyclohexadiene

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