# Changeset 393facf in sasmodels for sasmodels/models/rectangular_prism.py

Ignore:
Timestamp:
Nov 6, 2017 4:25:04 AM (5 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
Message:

update documentation for core_shell_parallelepiped, hollow_rectangular_prism and rectangular_prism

File:
1 edited

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Unmodified
 r8de1477 the prism (e.g. setting $b/a = 1$ and $c/a = 1$ and applying polydispersity to *a* will generate a distribution of cubes of different sizes). Note also that, contrary to :ref:parallelepiped, it does not compute the 2D scattering. that reference), with $\theta$ corresponding to $\alpha$ in that paper, and not to the usual convention used for example in the :ref:parallelepiped model. As the present model does not compute the 2D scattering, this has no further consequences. :ref:parallelepiped model. In this model the scattering from a massive parallelepiped with an units) *scale* represents the volume fraction (which is unitless). **The 2D scattering intensity is not computed by this model.** For 2d data the orientation of the particle is required, described using angles $\theta$, $\phi$ and $\Psi$ as in the diagrams below, for further details of the calculation and angular dispersions see :ref:orientation . The angle $\Psi$ is the rotational angle around the long *C* axis. For example, $\Psi = 0$ when the *B* axis is parallel to the *x*-axis of the detector. For 2d, constraints must be applied during fitting to ensure that the inequality $A < B < C$ is not violated, and hence the correct definition of angles is preserved. The calculation will not report an error, but the results may be not correct. .. figure:: img/parallelepiped_angle_definition.png Definition of the angles for oriented core-shell parallelepipeds. Note that rotation $\theta$, initially in the $xz$ plane, is carried out first, then rotation $\phi$ about the $z$ axis, finally rotation $\Psi$ is now around the axis of the cylinder. The neutron or X-ray beam is along the $z$ axis. .. figure:: img/parallelepiped_angle_projection.png Examples of the angles for oriented rectangular prisms against the detector plane.