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


Ignore:
Timestamp:
Nov 6, 2017 4:25:04 AM (5 years ago)
Author:
dirk
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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  • sasmodels/models/rectangular_prism.py

    r8de1477 r393facf  
    1212the prism (e.g. setting $b/a = 1$ and $c/a = 1$ and applying polydispersity 
    1313to *a* will generate a distribution of cubes of different sizes). 
    14 Note also that, contrary to :ref:`parallelepiped`, it does not compute 
    15 the 2D scattering. 
    1614 
    1715 
     
    2624that reference), with $\theta$ corresponding to $\alpha$ in that paper, 
    2725and 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. 
    3027 
    3128In this model the scattering from a massive parallelepiped with an 
     
    6562units) *scale* represents the volume fraction (which is unitless). 
    6663 
    67 **The 2D scattering intensity is not computed by this model.** 
     64For 2d data the orientation of the particle is required, described using 
     65angles $\theta$, $\phi$ and $\Psi$ as in the diagrams below, for further details 
     66of the calculation and angular dispersions see :ref:`orientation` . 
     67The 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 
     70For 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, 
     72but 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 
    6886 
    6987 
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