Solve a problem

Real questions.
Practical answers.

112 questions, grouped by what you see. Start with the thing that looks wrong; you should not need to know which chapter contains the answer.

Orientation map with a target grain marked for lift-out

Browse by area

Where is the problem?

Diffraction 19 Imaging & spectroscopy 22 EBSD / TKD 20 APT 14 FIB / specimen prep 9 Mechanics / tribology 21 All questions 112

Featured questions

Asked most often

DiffractionHow do I simulate the diffraction pattern of my own crystal?TEM & STEM Imaging & spectroscopyWhich reflections should I image to find a Burgers vector?TEM & STEM EBSD / TKDHow do I simulate an EBSD pattern for my phase?EBSD & TKD

Can you trust this result?

Check before you conclude

Before a number goes in a paper: these guides walk through what the instrument actually measured, which artefacts look like results, and what evidence would settle it.

GuideSAED Indexing, g-Vectors & Real vs. Fake SpotsInteractive guide to indexing SAED patterns by hand: measure g-vectors from spot ratio and angle, see whether those two numbers name one zone axis or several at your measurement precision, and score a twin, double diffraction and a second phase against the same extra spots.GuideWhen Forbidden Reflections AppearInteractive guide to forbidden reflections and superlattices in TEM: why spots are systematically absent, the mechanisms that make them appear (double diffraction, relrods, stacking faults), and a field guide to superlattices in metals and alloys: chemical ordering, the omega phase, long-period structures and their look-alikes.ToolQuantitative HAADFPut an experimental HAADF-STEM image on an absolute scale in the browser: normalise to the detector dark level and probe current, find and refine the atomic columns, integrate each column over a disc or its Voronoi cell, read the statistics, and compare with the fraction-versus-thickness curves exported by the SAED simulator to estimate thickness and the Z-contrast exponent.ToolBend ContoursBend contours simulated in the browser: pick one of 604 crystals or a CIF, a zone axis and how the foil is bent, and see the many-beam Bloch-wave rocking surface painted on the bent foil as bright-field and dark-field images with the contour pairs, higher orders, fringes and bend centre; move the holder tilt and watch the contours slide, read the radius of curvature from the spacing, and get the eleven most asked questions about bend contours answered.GuideHRTEM & FFTsInteractive guide to HRTEM and FFTs: a defocus/CTF lattice-image simulator with a true atom-column overlay, the Scherzer-defocus CTF explorer, measuring d-spacings from an FFT with a draggable ROI, how Fourier filtering can conjure fake lattices from noise, and FFT versus SAED.ToolWear Rate CalculatorTurn what you measured into every wear rate at once: a profile area, a mass loss, a ball scar diameter or a groove, with the load and the sliding distance, giving the wear rate, the specific wear rate in mm3/N.m, the dimensionless Archard coefficient and the wear depth, with the arithmetic on show. Includes the unit map for the forms these appear in and what ASTM G99 does and does not fix.

All troubleshooting resources

All 112 questions

Diffraction 19

TEMHow do I simulate the diffraction pattern of my own crystal?

TEMKinematic or dynamical: which simulation should I trust?

TEMHow do I calibrate the camera constant from a gold ring pattern?

TEMHow do I get the point group from a CBED pattern?

TEMHow do I turn a spot distance into a d-spacing?

TEMMy d-spacing matches three different phases. Now what?

TEMAre bend contours the same thing as Kikuchi lines?

TEMDo I need the camera length to index a SAED pattern?

TEMCan I trust a zone axis obtained from two reflections?

TEMTwin spot, double diffraction, or second phase?

TEMWhy are my diffraction spots streaked?

TEMHow do I get a sharp SAED pattern instead of a blurry one?

TEMWhy do only some of the spots my lattice predicts actually light up?

TEMWhy are forbidden reflections appearing in my SAED pattern?

TEMWhat does excitation error s_g actually mean?

TEMWhy does tilting one degree completely change a TEM diffraction pattern?

TEMHow do I tell a twin boundary from a low-angle grain boundary in a diffraction pattern?

TEMHow far off-zone am I?

TEMHow do I calculate TEM lamella thickness from CBED fringes?

Imaging & spectroscopy 22

TEMWhich reflections should I image to find a Burgers vector?

TEMWhy is my dislocation still visible when g.b = 0?

TEMIs my dislocation loop vacancy or interstitial?

TEMHow do I measure a d-spacing from an HRTEM image?

TEMHow do I turn HAADF grey levels into a number I can compare?

TEMHow do I get a composition from a core-loss edge?

TEMHow do I get a composition from an EDS spectrum of a thin foil?

TEMWhy do the dark lines move when I tilt the specimen a little?

TEMBend contour or thickness fringe: how do I tell them apart?

TEMHow do I get rid of bend contours so I can image dislocations?

TEMWhy is one grain (or one particle) dark and its neighbour bright?

TEMWhy does the same grain look bright in one image and dark in another?

TEMWhich STEM detector should I use: BF, ABF, ADF, or HAADF?

TEMWhy doesn't HAADF always follow Z-contrast?

TEMIs this contrast feature in my image a real signal or an artifact?

TEMWhy is my weak-beam dark-field image so dark, and what do I do about it?

TEMWhy doesn't the bright dislocation line sit exactly on the true dislocation core?

TEMWhy does my HRTEM FFT show rings instead of clean spots?

TEMWhat are those big Moiré fringes in my FFT, and are they a real superstructure?

TEMWhy is my FFT lying to me?

TEMWhy is my EELS thickness wrong?

TEMWhy does my EELS thickness change when I change the collection angle?

EBSD / TKD 20

EBSDHow do I simulate an EBSD pattern for my phase?

EBSDWhy does the simulated pattern look sharper than mine?

EBSDWhere in the sample do the electrons that form an EBSD pattern come from?

EBSDWhy are the bands bright in the middle with dark lines at the edges?

EBSDWhy does my simulated pattern show more fine lines than my measured one?

EBSDHow does EBSD indexing actually turn a Kikuchi pattern into an orientation?

EBSDWhat do CI and MAD actually tell me about how trustworthy an indexed point is?

EBSDWhy do two very different orientations sometimes show up as almost the same IPF color?

EBSDWhat does an IPF map never actually show me?

EBSDHow do I calculate the misorientation between two grains from EBSD data?

EBSDWhy does changing my grain-boundary misorientation threshold change the grain count on the exact same dataset?

EBSDShould twins be separate grains in grain-size analysis?

EBSDHow do I read a pole figure or an ODF section for texture components?

EBSDWhy does cleaning up my EBSD scan change my measured grain count and twin fraction?

EBSDMy grains are nanocrystalline: should I use bulk EBSD or TKD?

EBSDWhy is my TKD pattern worse after making the foil thinner?

EBSDWhy does my EBSD image quality (IQ) drop before indexing actually starts failing?

EBSDCan I just use an IQ map as a strain map?

EBSDWhy does pattern quality drop near a grain boundary?

EBSDWhy does KAM depend on step size, and can it measure dislocation density?

APT 14

APTWhy does APT resolve atomic planes in depth but blur features laterally?

APTWhy does a precipitate near my tip apex look distorted or magnified in the reconstruction?

APTIs this segregation real or local magnification?

APTWhy is my interface wider in APT than in TEM?

APTHow do I deal with overlapping peaks in my atom probe mass spectrum?

APTHow many atoms do I actually need before a composition number means something?

APTHow do I measure segregation at an interface with APT?

APTWhy does my proxigram change with the isoconcentration threshold?

APTIs Gibbsian interfacial excess more robust than peak segregation?

APTWhy is my mass peak tailing?

APTVoltage pulsing or laser pulsing: which should I use?

APTHow do I prepare a site-specific APT needle from a feature I care about, like a grain boundary?

APTCan I study the same feature with both APT and TEM?

APTWhere did my hydrogen come from?

FIB / specimen prep 9

In-situCan I just redefine ND during acquisition and then pick a grain that matches?

In-situWhat does R★ actually mean?

In-situWhat does the stage rotation achieve, physically?

In-situWhy not tilt the stage a few degrees and put the axis dead on the beam?

In-situDoes it matter how the sample happens to sit on the stub?

In-situDo I subtract the 70° EBSD tilt, or the 52° milling tilt, from my orientation data?

In-situTwo grains have almost the same Euler color, so they are almost the same orientation, right?

In-situWhich holder tilt fixes the leftover δ once the lamella is in the TEM?

In-situWhat if no grain in my map is within budget?

Mechanics / tribology 21

IndentationWhen does Oliver-Pharr give the wrong hardness?

IndentationHow flat does my surface have to be for nanoindentation?

IndentationWhy does the top of my unloading curve bend backwards?

IndentationIs this nanoindentation result usable?

TribologyWhy is the real contact area between two surfaces so much smaller than the apparent area?

TribologyHow do I know which wear mechanism, adhesive, abrasive, fatigue, or oxidative, actually dominates in my system?

TribologyHow do I get an actual wear depth in micrometers, not just a wear coefficient?

IndentationHow do I calculate hardness and modulus from a raw nanoindentation load-displacement curve?

IndentationHow much can an uncalibrated tip shape actually change my reported hardness?

IndentationWhen does Oliver-Pharr fail?

IndentationIs my hardness increasing at shallow indentation depth a real size effect or a blunt tip?

IndentationHow much do pile-up or sink-in actually change my contact-area estimate?

IndentationWhy does my modulus change with depth?

IndentationHow far from an interface must I indent?

IndentationHow do I get a stress-strain curve out of a spherical indentation?

IndentationWhy do different fracture-toughness equations give different answers for the same crack?

IndentationWhat does a pop-in actually prove?

IndentationWhich nanoindentation loading mode should I actually use for my question?

ScratchWhat do Lc1, Lc2 and Lc3 in a progressive-load scratch test actually mean?

ScratchWhy does my scratch hardness number depend on how I measure the groove width?

ScratchWhy isn't the hardest coating always the most wear-resistant one?