Editing Electron diffraction (section)

==== Precession electron diffraction ====
{{main|Precession electron diffraction}}
{{anchor|Figure 19}}[[File:Precession Electron Diffraction (White).gif|Figure 19: Geometry of electron beam in precession electron diffraction. Original diffraction patterns collected by C.S. Own at Northwestern University<ref name="thesis">Own, C. S.: PhD thesis, System Design and Verification of the Precession Electron Diffraction Technique, Northwestern University, 2005, http://www.numis.northwestern.edu/Research/Current/precession.shtml</ref>|thumb|300x300px|alt=An animation showing how rotating the incident beam direction can build up in a precession experiment.]]
Precession electron diffraction (PED), invented by Roger Vincent and [[Paul Midgley]] in 1994,<ref>{{Cite journal |last1=Vincent |first1=R. |last2=Midgley |first2=P.A. |date=1994 |title=Double conical beam-rocking system for measurement of integrated electron diffraction intensities |url=https://linkinghub.elsevier.com/retrieve/pii/0304399194900396 |journal=Ultramicroscopy |language=en |volume=53 |issue=3 |pages=271–282 |doi=10.1016/0304-3991(94)90039-6|url-access=subscription }}</ref> is a method to collect electron diffraction patterns in a [[transmission electron microscope]] (TEM). The technique involves rotating (precessing) a tilted incident electron beam around the central axis of the microscope, compensating for the tilt after the sample so a spot diffraction pattern is formed, similar to a SAED pattern. However, a PED pattern is an integration over a collection of diffraction conditions, see [[#Figure 19|Figure 19]]. This integration produces a quasi-kinematical [[diffraction pattern]] that is more suitable<ref>{{Cite journal |last1=Gjønnes |first1=J. |last2=Hansen |first2=V. |last3=Berg |first3=B. S. |last4=Runde |first4=P. |last5=Cheng |first5=Y. F. |last6=Gjønnes |first6=K. |last7=Dorset |first7=D. L. |last8=Gilmore |first8=C. J. |date=1998|title=Structure Model for the Phase AlmFe Derived from Three-Dimensional Electron Diffraction Intensity Data Collected by a Precession Technique. Comparison with Convergent-Beam Diffraction |url=https://scripts.iucr.org/cgi-bin/paper?S0108767397017030 |journal=Acta Crystallographica Section A |volume=54 |issue=3 |pages=306–319 |doi=10.1107/S0108767397017030|bibcode=1998AcCrA..54..306G |url-access=subscription }}</ref> as input into [[direct methods (crystallography)|direct methods]] algorithms using electrons<ref name="Sufficient">{{Cite journal |last1=Marks |first1=L.D. |last2=Sinkler |first2=W. |date=2003 |title=Sufficient Conditions for Direct Methods with Swift Electrons |url=https://www.cambridge.org/core/product/identifier/S1431927603030332/type/journal_article |journal=Microscopy and Microanalysis |language=en |volume=9 |issue=5 |pages=399–410 |doi=10.1017/S1431927603030332 |pmid=19771696 |bibcode=2003MiMic...9..399M |s2cid=20112743 |issn=1431-9276|url-access=subscription }}</ref><ref name="White">{{Cite journal |last1=White |first1=T.A. |last2=Eggeman |first2=A.S. |last3=Midgley |first3=P.A. |date=2010 |title=Is precession electron diffraction kinematical? Part I |url=https://linkinghub.elsevier.com/retrieve/pii/S030439910900240X |journal=Ultramicroscopy |language=en |volume=110 |issue=7 |pages=763–770 |doi=10.1016/j.ultramic.2009.10.013|pmid=19910121 |url-access=subscription }}</ref> to determine the [[crystal structure]] of the sample. Because it avoids many dynamical effects it can also be used to better identify crystallographic phases.<ref>{{Cite journal |last1=Moeck |first1=Peter |last2=Rouvimov |first2=Sergei |date=2010 |title=Precession electron diffraction and its advantages for structural fingerprinting in the transmission electron microscope |journal=Zeitschrift für Kristallographie |language=en |volume=225 |issue=2–3 |pages=110–124 |doi=10.1524/zkri.2010.1162 |bibcode=2010ZK....225..110M |s2cid=52059939 |issn=0044-2968|doi-access=free }}</ref>