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Ben Torralva

Bio: Ben Torralva is an academic researcher from University of Michigan. The author has contributed to research in topics: Laser & Femtosecond. The author has an hindex of 18, co-authored 45 publications receiving 1054 citations. Previous affiliations of Ben Torralva include Chongqing University of Posts and Telecommunications & Lawrence Livermore National Laboratory.

Papers
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Journal ArticleDOI
16 Sep 2005-Science
TL;DR: Molecular dynamics simulations of nanocrystalline copper under shock loading show an unexpected ultrahigh strength behind the shock front, with values up to twice those at low pressure.
Abstract: Molecular dynamics simulations of nanocrystalline copper under shock loading show an unexpected ultrahigh strength behind the shock front, with values up to twice those at low pressure. Partial and perfect dislocations, twinning, and debris from dislocation interactions are found behind the shock front. Results are interpreted in terms of the pressure dependence of both deformation mechanisms active at these grain sizes, namely dislocation-based plasticity and grain boundary sliding. These simulations, together with new shock experiments on nanocrystalline nickel, raise the possibility of achieving ultrahard materials during and after shock loading.

287 citations

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TL;DR: The DTEM as mentioned in this paper is a single-shot in situ transmission electron microscope (TEM) modified to drive material processes with a nanosecond laser, "pump" pulse and measure it shortly afterward with a 30-ns-long probe pulse of ∼107 electrons.
Abstract: A dynamic transmission electron microscope (DTEM) has been designed and implemented to study structural dynamics in condensed matter systems. The DTEM is a conventional in situ transmission electron microscope (TEM) modified to drive material processes with a nanosecond laser, “pump” pulse and measure it shortly afterward with a 30-ns-long probe pulse of ∼107 electrons. An image with a resolution of <20nm may be obtained with a single pulse, largely eliminating the need to average multiple measurements and enabling the study of unique, irreversible events with nanosecond- and nanometer-scale resolution. Space charge effects, while unavoidable at such a high current, may be kept to reasonable levels by appropriate choices of operating parameters. Applications include the study of phase transformations and defect dynamics at length and time scales difficult to access with any other technique. This single-shot approach is complementary to stroboscopic TEM, which is capable of much higher temporal resolution but is restricted to the study of processes with a very high degree of repeatability.

133 citations

Journal ArticleDOI
TL;DR: The generation and control of electron pulses in the TEM to obtain a temporal resolution <10(-6)s will be described and the effect of the pulse duration and current density on the spatial resolution of the instrument will be examined.

92 citations

Journal ArticleDOI
TL;DR: In this paper, the deformation mechanism of nanocrystalline Ni at ultrahigh strain rates (>107s−1) was investigated, and it was shown that dislocation activity is a prevalent deformation mechanisms for the grain sizes studied.
Abstract: The deformation mechanism of nanocrystalline Ni (with grain sizes in the range of 30–100 nm) at ultrahigh strain rates (>107s−1) was investigated. A laser-driven compression process was applied to achieve high pressures (20–70 GPa) on nanosecond timescales and thus induce high-strain-rate deformation in the nanocrystalline Ni. Postmortem transmission electron microscopy examinations revealed that the nanocrystalline structures survive the shock deformation, and that dislocation activity is a prevalent deformation mechanism for the grain sizes studied. No deformation twinning was observed even at stresses more than twice the threshold for twin formation in micron-sized polycrystals. These results agree qualitatively with molecular dynamics simulations and suggest that twinning is a difficult event in nanocrystalline Ni under shock-loading conditions.

76 citations

Journal ArticleDOI
TL;DR: In this paper, a simulation of the one-electron Hamiltonian and ion-ion interactions was performed for the cis-trans isomerization of butadiene following a femtosecond-scale laser pulse.
Abstract: Detailed simulations are reported for the dynamics of electrons and nuclei during the cis—trans isomerization of butadiene following a femtosecond-scale laser pulse. Our technique, semiclassical electron-radiationion dynamics (SERID), is fully described in the text. The one-electron Hamiltonian and ion—ion interactions employed in the present work are density-functional based. Following excitation of electrons by the laser pulse, all three C—C bonds in the butadiene molecule become longer, as electrons are promoted from the HOMO to both the LUMO and LUMO+1 levels. In the excited electronic state, the molecule rotates about all of its three C—C bonds. There are then non-adiabatic events near avoided crossings, with electronic transitions to the ground state via creation of vibrational excitations. The molecule continues to twist around the central bond and one of the terminal C—C bonds, until the trans-conformation is achieved. Various features in the behaviour of the vibrational modes can also be...

57 citations


Cited by
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Journal ArticleDOI
01 Jan 1958-Nature
TL;DR: In this paper, the authors present an overview of the relationship between organic chemistry and natural products, focusing on the Stereochemistry and the Chemistry of Natural Products (SCHP).
Abstract: Organic Chemistry By Dr. I. L. Finar. Vol. 2: Stereochemistry and the Chemistry of Natural Products. Pp. xi + 733. (London and New York: Longmans, Green and Co., Ltd., 1956.) 40s. net.

1,037 citations

Journal ArticleDOI
TL;DR: In this paper, a review of deformation twinning in nanocrystalline materials is presented, including deformation twins observed by molecular dynamics simulations and experiments, twinning mechanisms, factors affecting the twinning, analytical models on the nucleation and growth of deformations, interactions between twins and dislocations, and the effects of twins on mechanical and other properties.

1,015 citations

Journal ArticleDOI
TL;DR: The framework and the adaptive algorithms enable physics-based space weather modeling and even short-term forecasting and the algorithms of BATL, the Block-Adaptive Tree Library, are described and its efficiency and scaling properties for various problems are described.

693 citations

Journal ArticleDOI
TL;DR: In this article, the current state in the field of laser-induced periodic surface structures (LIPSS) is reviewed, and the formation mechanisms are analyzed in ultrafast time-resolved scattering, diffraction, and polarization constrained double-pulse experiments.
Abstract: Laser-induced periodic surface structures (LIPSS, ripples) are a universal phenomenon and can be generated on almost any material upon irradiation with linearly polarized radiation. With the availability of ultrashort laser pulses, LIPSS have gained an increasing attraction during the past decade, since these structures can be generated in a simple single-step process, which allows a surface nanostructuring for tailoring optical, mechanical, and chemical surface properties. In this study, the current state in the field of LIPSS is reviewed. Their formation mechanisms are analyzed in ultrafast time-resolved scattering, diffraction, and polarization constrained double-pulse experiments. These experiments allow us to address the question whether the LIPSS are seeded via ultrafast energy deposition mechanisms acting during the absorption of optical radiation or via self-organization after the irradiation process. Relevant control parameters of LIPSS are identified, and technological applications featuring surface functionalization in the fields of optics, fluidics, medicine, and tribology are discussed.

607 citations