Figure 3.

The description of diffraction geometry for the rotation method using dxtbx models. A monochromatic X-ray beam is represented by the wavevector , which intersects a sample rotation axis, given by the unit vector , at the origin of the reciprocal laboratory coordinate system. An abstract detector plane k is described in the real space laboratory coordinate system with an origin vector and a pair of orthogonal basis vectors . The detector model provides a pair of limits, and , forming a bounded rectangular panel within the plane. A crystal model complements the dxtbx geometry models, with its setting expressed in a ϕ-axis frame (aligned to the reciprocal laboratory frame at a rotation angle of ϕ = 0°) by the setting matrix , following the Protein Data Bank (http://www.pdb.org/pdb/home/home.do) convention. Diffraction is represented by the wavevector , which may be extended to the point at which it meets the detector panel, in the panel’s coordinate frame.