# Changeset 96153e4 in sasmodels for sasmodels/models/parallelepiped.py

Ignore:
Timestamp:
May 20, 2018 11:22:28 PM (4 years ago)
Branches:
master, core_shell_microgels, magnetic_model, ticket-1257-vesicle-product, ticket_1156, ticket_1265_superball, ticket_822_more_unit_tests
Children:
fc7bcd5
Parents:
c64a68e
Message:

more corrections and normalizations

Addreses #896. Brings parallelepiped and core-shell parallelepiped more
into line with each other and corrects angle definitions refering to
orietnational distribution docs for details. Still need to sort out
with Paul Kienzle the proper order the angles are applied.

File:
1 edited

### Legend:

Unmodified
 rb343226 The three dimensions of the parallelepiped (strictly here a cuboid) may be given in *any* size order. To avoid multiple fit solutions, especially with Monte-Carlo fit methods, it may be advisable to restrict their ranges. There may be a number of closely similar "best fits", so some trial and error, or fixing of some dimensions at expected values, may help. given in *any* size order as long as the particles are randomly oriented (i.e. take on all possible orientations see notes on 2D below). To avoid multiple fit solutions, especially with Monte-Carlo fit methods, it may be advisable to restrict their ranges. There may be a number of closely similar "best fits", so some trial and error, or fixing of some dimensions at expected values, may help. The form factor is normalized by the particle volume and the 1D scattering of the calculation and angular dispersions see :ref:orientation . .. Comment by Miguel Gonzalez: The following text has been commented because I think there are two mistakes. Psi is the rotational angle around C (but I cannot understand what it means against the q plane) and psi=0 corresponds to a||x and b||y. The angle $\Psi$ is the rotational angle around the $C$ axis against the $q$ plane. For example, $\Psi = 0$ when the $B$ axis is parallel to the $x$-axis of the detector. The angle $\Psi$ is the rotational angle around the $C$ axis. For $\theta = 0$ and $\phi = 0$, $\Psi = 0$ corresponds to the $B$ axis of the particle to obtain the final orientation of the parallelepiped. .. note:: 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. .. _parallelepiped-orientation: