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![[Figure 3]](rw5055fig3mag.jpg)
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Figure 3
Three orthogonal and right-handed coordinate systems for a standard four-circle diffractometer with Euler angles 2θ, ω, χ and φ. The coordinate system convention is as proposed in the SPEC software. When the coordinates are all zero they are coincident for the three coordinate systems. (a) The laboratory coordinate system xyz (fixed frame in laboratory) and the diffractometer coordinate system (angles as shown). Circles 2θ, ω and φ are defined as right handed and χ is left handed as indicated. (b) The sample coordinate system (fixed with sample natural axes). The scattering vector q, along the normal of the Bragg planes, is oriented with angles χ and φ before it is rotated into the Bragg condition. The component qz is along the z direction and qφ in the xy plane. (c) The Bragg condition is satisfied as shown. The scattering vector magnitude q is equal to the reciprocal-space vector, i.e. 1/d, the reciprocal of the Bragg plane spacing. When ω = θ, α = β = θ, this is a symmetrical setting and ω needs to be rotated to satisfy the Bragg condition. |
![[Figure 3]](rw5055fig3.jpg)
 | JOURNAL OF APPLIED CRYSTALLOGRAPHY |
ISSN: 1600-5767
