See for example:

http://prism.mit.edu/xray/oldsite/Basics%20of%20X-Ray%20Powder%20Diffraction.pdf

https://www.youtube.com/watch?annotation_id=annotation_2363264245&feature=iv&src_vid=wkusJqpLPMo&v=wkusJqpLPMo#t=4.5s

Dear Gerhard Martens

Thanks for your response. Could you point me to some resource on terminologies (e.g. what are radial, omega, angular, theta-2theta scans, etc.)?

Best,

Prabhu

The following presentation goes more into the terminologies which you are asking for:

https://mrl.illinois.edu/sites/default/files/AMC/downloads/AMC-Workshop-2012_Tutorial-4_XRD.pdf

and in (around page 240):

https://www.chem.uci.edu/~lawm/263%204.pdf

Thanks Gerhard Martens

Add up to 15 topics up top to increase circulation among expert RG members.

See following question for potential relevant additional topics:

https://www.researchgate.net/post/How_do_I_calibrate_the_diffractometer_2Theta_angles_with_this_powder_diffractogram_of_corundum_standard_from_a_Bruker_D8_XRD_instrument

One has to understand the intensity in terms of form factor & structure factor.Then only one can establish a reasonable correlation between Two Theta & Intensity. Although it is tough to do but one must have to understand the basics.

"what are radial, omega, angular, theta-2theta scans" - Different methods to measure and quantify the reciprocal space. Experimental methods to make measurements in reciprocal space (theta/omega, phi, chi) for correlation with nano structural parameters (real space). I'd guess "radial" would probably mean along the diffractometer radius while "angular" meaning along the diffractometer equatorial plane for a fixed diffractometer radius.

The nomenclature is based on convention. Generally there are:

Assuming that the incident beam direction is perpendicular to the diffractometer axis and parallel to the diffractometer plane.

Omega Scan: For a fixed detector 2theta, the sample surface is rotated about the diffractometer axis.

Theta-2theta or 2theta-theta - is a coupled scan and the nomenclature depends on the angle being monitored or reported. The fist mentioned is generally the one being reported.

Bottom-line: These real time NDE XRD scans can be eventually converted to "crystallographic lattice dilatation", "crystallographic defect density", "relative layer thickness", and other nano structural characteristics for the sampled voxel in the case of advanced multilayered epitaxial specimen.

Note: Image attached is extracted from previously posted info.

Thanks Ravi Ananth and Dillip KUMAR Bisoyi !

The fundamental principle on which XRD relies is the Bragg's law only.

Bragg's law i.e. 2dsintheta = nLambda

Lambda is the wavelength of the prob & Theta is the Glancing angle

Thanks Dillip KUMAR Bisoyi !

The "deviation" from ideal Bragg condition (as noted by @Dillip Kumar Bisoyi) is directly related to the local Nano structure i.e., lattice dilatation, defect density, and individual layer thickness including the ability to detect defect morphology.

It would be best practice to calibrate each individual XRD instrument with a reference diffractogram. The choice of the "reference diffractogram" is quintessential in the quest to correlate experimental observations with Nano structural interpretations. Some potential options include numerical simulations and "known reference samples". In either case, it is the deviation from the "reference" that may be usable for interpreting relative Nano structure.

The XRD approach would certainly have to be calibrated & corroborated with AFM, TEM, SEM, PL etc. The NDE character, with little or no sample prep, of XRD makes it the perfect choice in R&D and manufacturing applications for Nano structural QC of both mono-crystalline substrates as well as advanced multilayered epitaxial specimen. Powders are a different matter altogether :-)

Make this discussion a great comprehensive resource. Add to it what else you have found.