Changeset 393facf in sasmodels for sasmodels/models/rectangular_prism.py
- Timestamp:
- Nov 6, 2017 2:25:04 AM (6 years ago)
- Branches:
- master, core_shell_microgels, magnetic_model, ticket-1257-vesicle-product, ticket_1156, ticket_1265_superball, ticket_822_more_unit_tests
- Children:
- 49eb251
- Parents:
- 8de1477
- File:
-
- 1 edited
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sasmodels/models/rectangular_prism.py
r8de1477 r393facf 12 12 the prism (e.g. setting $b/a = 1$ and $c/a = 1$ and applying polydispersity 13 13 to *a* will generate a distribution of cubes of different sizes). 14 Note also that, contrary to :ref:`parallelepiped`, it does not compute15 the 2D scattering.16 14 17 15 … … 26 24 that reference), with $\theta$ corresponding to $\alpha$ in that paper, 27 25 and not to the usual convention used for example in the 28 :ref:`parallelepiped` model. As the present model does not compute 29 the 2D scattering, this has no further consequences. 26 :ref:`parallelepiped` model. 30 27 31 28 In this model the scattering from a massive parallelepiped with an … … 65 62 units) *scale* represents the volume fraction (which is unitless). 66 63 67 **The 2D scattering intensity is not computed by this model.** 64 For 2d data the orientation of the particle is required, described using 65 angles $\theta$, $\phi$ and $\Psi$ as in the diagrams below, for further details 66 of the calculation and angular dispersions see :ref:`orientation` . 67 The angle $\Psi$ is the rotational angle around the long *C* axis. For example, 68 $\Psi = 0$ when the *B* axis is parallel to the *x*-axis of the detector. 69 70 For 2d, constraints must be applied during fitting to ensure that the inequality 71 $A < B < C$ is not violated, and hence the correct definition of angles is preserved. The calculation will not report an error, 72 but the results may be not correct. 73 74 .. figure:: img/parallelepiped_angle_definition.png 75 76 Definition of the angles for oriented core-shell parallelepipeds. 77 Note that rotation $\theta$, initially in the $xz$ plane, is carried out first, then 78 rotation $\phi$ about the $z$ axis, finally rotation $\Psi$ is now around the axis of the cylinder. 79 The neutron or X-ray beam is along the $z$ axis. 80 81 .. figure:: img/parallelepiped_angle_projection.png 82 83 Examples of the angles for oriented rectangular prisms against the 84 detector plane. 85 68 86 69 87
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