XRD basics

Multiple Choice

Why are X-ray diffraction methods considered the most effective for determining the crystal structure of materials?

• Because they can identify chemical compounds from their crystalline structure, not from their compositions of chemical elements.

• Because they are the only method available for material characterization.

• Because they use high-energy beams that penetrate all materials.

• Because they are faster than other diffraction methods.

Open Ended

Explain the significance of generating X-rays with a range of wavelengths and the role of characteristic X-ray generation in material characterization.

Multiple Choice

Which of the following statements best explains why the intensity of Kα X-rays is higher than that of Kβ X-rays?

• K shell vacancy energy is higher than M shell vacancy energy

• Kβ X-rays have longer wavelengths than Kα X-rays

• Kα X-rays are generated from L to K shell transitions, while Kβ from M to K

• Kα X-rays are always monochromatic

Multiple Choice

Based on Table 2.1, which anode material requires the highest optimum voltage for generating characteristic X-rays?

• Cr

• Fe

• Cu

• Mo

Fill in the Blanks

The radius of the Ewald sphere is given by

in reciprocal space.

Multiple Choice

Which of the following statements about the reciprocal lattice is correct?

• Each lattice point in reciprocal space represents a crystal plane (hkl) in real space.

• The magnitude of a vector in reciprocal lattice equals the square of the plane spacing in real space.

• The reciprocal lattice is always orthogonal to the real lattice.

• The direction of d*_hkl is parallel to the crystal plane (hkl).

Multiple Choice

Which condition must be satisfied for a reciprocal lattice point to touch the surface of the Ewald sphere and produce a diffraction spot?

• The reciprocal lattice point must be at the origin

• The reciprocal lattice point must be perpendicular to the incident beam

• The reciprocal lattice point must satisfy Bragg's Law

• The reciprocal lattice point must be parallel to the crystal zone axis

Multiple Select

Which of the following statements about the Debye ring pattern observed in powder X-ray diffraction is/are correct?

• It results from randomly oriented crystals in the powder specimen.

• It is produced when reciprocal lattice points touch the Ewald sphere surface.

• It is only observed with single crystals.

• It is equivalent to rotating a reciprocal lattice along an incident beam axis.

Open Ended

Explain how the Ewald sphere method helps in detecting crystal planes using diffraction, and describe its significance in electron microscopy.

Multiple Choice

The minimum wavelength (λ) of continuous X-rays generated in an X-ray tube is determined by the maximum acceleration voltage of electrons. According to the equation λ = 1.2398 × 10³ / V (nm), what happens to the minimum wavelength if the acceleration voltage is increased?

• The minimum wavelength increases

• The minimum wavelength decreases

• The minimum wavelength remains the same

• The minimum wavelength fluctuates unpredictably

Open Ended

Summarize the main differences between spectroscopic and photographic X-ray diffraction methods as discussed in the chapter.