Changeset eda8b30 in sasmodels for sasmodels/models/parallelepiped.py
- Timestamp:
- Oct 28, 2017 4:42:15 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:
- 5f8b72b
- Parents:
- da5536f
- File:
-
- 1 edited
Legend:
- Unmodified
- Added
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sasmodels/models/parallelepiped.py
rca04add reda8b30 74 74 $S(q)$ when $P(q) \cdot S(q)$ is applied. 75 75 76 To provide easy access to the orientation of the parallelepiped, we define 77 three angles $\theta$, $\phi$ and $\Psi$. The definition of $\theta$ and 78 $\phi$ is the same as for the cylinder model (see also figures below).76 For 2d data the orientation of the particle is required, described using 77 angles $\theta$, $\phi$ and $\Psi$ as in the diagrams below, for further details 78 of the calculation and angular dispersions see :ref:`orientation` . 79 79 80 80 .. Comment by Miguel Gonzalez: … … 89 89 The angle $\Psi$ is the rotational angle around the $C$ axis. 90 90 For $\theta = 0$ and $\phi = 0$, $\Psi = 0$ corresponds to the $B$ axis 91 oriented parallel to the y-axis of the detector with $A$ along the z-axis.91 oriented parallel to the y-axis of the detector with $A$ along the x-axis. 92 92 For other $\theta$, $\phi$ values, the parallelepiped has to be first rotated 93 $\theta$ degrees around $z$ and $\phi$ degrees around $y$, 94 before doing a final rotation of $\Psi$ degrees around the resulting $C$ to 95 obtain the final orientation of the parallelepiped. 96 For example, for $\theta = 0$ and $\phi = 90$, we have that $\Psi = 0$ 97 corresponds to $A$ along $x$ and $B$ along $y$, 98 while for $\theta = 90$ and $\phi = 0$, $\Psi = 0$ corresponds to 99 $A$ along $z$ and $B$ along $x$. 93 $\theta$ degrees in the $z-x$ plane and then $\phi$ degrees around the $z$ axis, 94 before doing a final rotation of $\Psi$ degrees around the resulting $C$ axis 95 of the particle to obtain the final orientation of the parallelepiped. 100 96 101 97 .. _parallelepiped-orientation: … … 114 110 (When $\theta = \phi = 0$ these are parallel to the $Y$ and $X$ axes of the instrument.) The third orientation distribution, in $\psi$, is 115 111 about the $c$ axis of the particle, perpendicular to the $a$ x $b$ face. Some experimentation may be required to 116 understand the 2d patterns fully. (Earlier implementations had numerical integration issues in some circumstances when orientation 117 distributions passed through 90 degrees, such situations, with very broad distributions, should still be approached with care.) 118 112 understand the 2d patterns fully as discussed in :ref:`orientation` . 119 113 120 114 For a given orientation of the parallelepiped, the 2D form factor is
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