Single-crystal diffraction

Monochromatic beam (wavelength λ). A reflection hkl appears when its reciprocal-lattice point lies on the Ewald sphere of radius 1/λ. Rotate or oscillate the crystal with the goniometer to bring points onto the sphere, and record the spots on the detector.

Crystal system Bravais lattice

Lattice parameters

a (Å)

b (Å)

c (Å)

α (°)

β (°)

γ (°)

Range (h, k, l): min, max

h k l

Only lattice-centring extinctions are applied (no glide planes or screw axes).

Beam and crystal

λ (Å) Mosaic 1.00° B (Å²) 0.0

Mosaic spread Δω turns each reciprocal point into a small cap of radius |g|·Δω/2: the reflection diffracts while the cap touches the Ewald sphere, and spots grow at high angle. B is a Debye–Waller factor: intensities fall as exp(−B|g|²/2).

Goniometer

φ 0.0° χ 0.0° ω 0.0° Crystal orientation at φ = χ = ω = 0

R = Ω·Χ·Φ. The two orientation conventions differ only for non-orthogonal cells (hexagonal, trigonal, monoclinic, triclinic).

ω scan

Mode

Width (°)

Speed 5.0°/s

Display

Show only diffracting points

Diffracted beams

Limiting sphere

Real axes a, b, c (directions)

Detector

Distance (mm) Width (mm) Angle 2θ_D (°)

Show detector in 3D

Detector image (inset)

The angle 2θ_D swings the detector about the vertical axis through the crystal (0° = transmission, 180° = back-reflection). Click a spot in the inset to select it; drag the inset's lower-left corner to resize it.

Integration

Integrate (accumulate spots on the detector)

Stop after (s), 0 = never

While Integrate is on, every reflection that crosses the Ewald sphere is recorded (yellow); cyan rings are spots diffracting now. Turning Integrate on starts the ω scan if it is paused, and pauses it again when integration stops. Recorded spots stay on the detector when you move it; a new wavelength or a new lattice clears them.

Click a reciprocal lattice point.