A practical method to detect and correct for lens distortion in the TEM

Capitani, Giancarlo; Oleynikov, Peter; Hovmöller, Sven; Mellini, Marcello

doi:10.1016/j.ultramic.2005.06.003

Cited by 57 publications

(49 citation statements)

References 23 publications

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“…A method of correcting for eccentricity was employed [14] followed by recalibration of the camera constant. Based on this methodology and its application to numerous selected-area electron diffraction patterns from this microscope, the upper limits of uncertainties for interplanar spacings and angles were estimated to be ±0.003 nm and ±2 o .…”

Section: Methodsmentioning

confidence: 99%

A Two-Tilt Analysis of Electron Diffraction Patterns from Transition-Iron-Carbide Precipitates Formed During Tempering of 4340 Steel

Thompson

2016

Metallogr. Microstruct. Anal.

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Fine-scale transition-iron-carbide precipitates in a lath martensitic microstructure of 4340 steel tempered at 200°C for 1 h were examined via imaging and electron diffraction techniques with a transmission electron microscope. Region-to-region variations were eliminated by analyzing a small volume of material (about 0.03 lm 3 ) at two tilt conditions. Geometric analyses showed that measured interplanar spacings compared favorably with accepted values from both epsilon-carbide and eta-carbide phases (within 1%), whereas measured interplanar angles were within 1-2% of accepted values. Centered-dark-field imaging identified precisely which reflections were produced from a single group of small precipitates (each about 10 nm in diameter). Consistent indexing schemes are provided for epsilon-and eta-carbide, including the proper angular relationship between the two tilt conditions. An interzonal angle of 17.9 o ± 0.1 o was determined for both candidate phases. The orientation relationship between the observed transition-iron-carbide phase and martensite was determined, and confirmed previous results reported for both carbide phases. Diffracted intensities of several reflections were estimated and compared favorably with those calculated from structure factors derived from idealized crystal structures of both transition-iron-carbide phases. All results are shown to be near-equally consistent with a hexagonal epsilon-carbide phase and an orthorhombic eta-carbide phase.

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Section: Methodsmentioning

confidence: 99%

A Two-Tilt Analysis of Electron Diffraction Patterns from Transition-Iron-Carbide Precipitates Formed During Tempering of 4340 Steel

Thompson

2016

Metallogr. Microstruct. Anal.

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“…Owing to the characteristics of the various experimental setups and/or the recording of the diffraction patterns, image distortions will generally occur not only in LEED 2,[7][8][9][10] but also in other diffraction methods. [11][12][13][14] Depending on the purpose of investigation, for example, when measuring lattice parameters and strain or when classifying the coincidence of an epitaxial organic layer, the distortions must be corrected in order to make these measurements meaningful.…”

Section: Introductionmentioning

confidence: 99%

“…15,16 In a few cases, detailed information on the applied algorithm and an estimate of its accuracy are given for specific (e.g., elliptical) distortions only. 12,13,17 In the case of X-ray diffraction Chung et al developed a method which is in principle capable of accounting for any type of deviation from the ideal diffraction pattern, i.e., also asymmetric distortion. 11 Yet, their method is meant to rectify distortions due to the imaging device only, in their case a charge-coupled device (CCD) with a 5:1 tapered fiber-optic coupling.…”

Section: Introductionmentioning

confidence: 99%

Determination and correction of distortions and systematic errors in low-energy electron diffraction

Helgert

Meißner

Zwick

et al. 2013

Review of Scientific Instruments

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We developed and implemented an algorithm to determine and correct systematic distortions in low-energy electron diffraction (LEED) images. The procedure is in principle independent of the design of the apparatus (spherical or planar phosphorescent screen vs. channeltron detector) and is therefore applicable to all device variants, known as conventional LEED, micro-channel plate LEED, and spot profile analysis LEED. The essential prerequisite is a calibration image of a sample with a well-known structure and a suitably high number of diffraction spots, e.g., a Si(111)-7×7 reconstructed surface. The algorithm provides a formalism which can be used to rectify all further measurements generated with the same device. In detail, one needs to distinguish between radial and asymmetric distortion. Additionally, it is necessary to know the primary energy of the electrons precisely to derive accurate lattice constants. Often, there will be a deviation between the true kinetic energy and the value set in the LEED control. Here, we introduce a method to determine this energy error more accurately than in previous studies. Following the correction of the systematic errors, a relative accuracy of better than 1% can be achieved for the determination of the lattice parameters of unknown samples.

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“…Small variations of magnification and distortion might require per-micrograph or per-particle level correction [16*,41 *]. Correction of additional distortions such as spiral, barrel, and pincushion [42] might become essential.…”

Section: Atomic Structures Of Jumbo Viruses (>100nm)mentioning

confidence: 99%

Atomic cryo-EM structures of viruses

Jiang

Tang

2017

Current Opinion in Structural Biology

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During the development of single particle cryo-EM in past five decades, icosahedral viruses have led the resolution progress owing to their large mass and high symmetry. Many technical advances in cryo-EM were first established with viruses. Since reaching ~4 Å resolution in 2008, it has become a relatively routine task to solve the atomic structure of isolated viruses. The future of structural virology will be increasingly focused on remaining challenges including solving structures of jumbo viruses, intermediate functional states during assembly, maturation, and infection, and in situ structures. Recent demonstrations of near-atomic resolution structure with electron tomography and sub-tomogram averaging opens a new direction for high resolution studies of pleomorphic viruses and the pleomorphic states of icosahedral viruses that have defied past efforts using the single particle cryo-EM approach.

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A practical method to detect and correct for lens distortion in the TEM

Cited by 57 publications

References 23 publications

A Two-Tilt Analysis of Electron Diffraction Patterns from Transition-Iron-Carbide Precipitates Formed During Tempering of 4340 Steel

A Two-Tilt Analysis of Electron Diffraction Patterns from Transition-Iron-Carbide Precipitates Formed During Tempering of 4340 Steel

Determination and correction of distortions and systematic errors in low-energy electron diffraction

Atomic cryo-EM structures of viruses

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