Changeset 96153e4 in sasmodels
 Timestamp:
 May 20, 2018 11:22:28 PM (3 months ago)
 Branches:
 master, ESS_GUI, beta_approx, beta_approx_lazy_results, beta_approx_new_R_eff, doc_update, ticket1104resolution, ticket1112, ticket1142pluginreload, ticket1148Sqscalebackground, ticket608userdefinedweights
 Children:
 fc7bcd5
 Parents:
 c64a68e
 Location:
 sasmodels/models
 Files:

 2 edited
Legend:
 Unmodified
 Added
 Removed

sasmodels/models/core_shell_parallelepiped.py
r5bc6d21 r96153e4 4 4 5 5 Calculates the form factor for a rectangular solid with a coreshell structure. 6 The thickness and the scattering length density of the shell or 7 "rim" can be different on each (pair) of faces. 6 The thickness and the scattering length density of the shell or "rim" can be 7 different on each (pair) of faces. The three dimensions of the core of the 8 parallelepiped (strictly here a cuboid) may be given in *any* size order as 9 long as the particles are randomly oriented (i.e. take on all possible 10 orientations see notes on 2D below). To avoid multiple fit solutions, e 11 specially with MonteCarlo fit methods, it may be advisable to restrict their 12 ranges. There may be a number of closely similar "best fits", so some trial and 13 error, or fixing of some dimensions at expected values, may help. 8 14 9 15 The form factor is normalized by the particle volume $V$ such that … … 18 24 pulled out of the form factor term due to the multiple slds in the model. 19 25 20 The core of the solid is defined by the dimensions $A$, $B$, $C$ such that21 $A < B < C$.26 The core of the solid is defined by the dimensions $A$, $B$, $C$ here shown 27 such that $A < B < C$. 22 28 23 29 .. figure:: img/parallelepiped_geometry.jpg … … 104 110 ~~~~~~~~~~~~~ 105 111 106 If the scale is set equal to the particle volume fraction, $\phi$, the returned107 value is the scattered intensity per unit volume, $I(q) = \phi P(q)$. However,108 **no interparticle interference effects are included in this calculation.**109 110 112 There are many parameters in this model. Hold as many fixed as possible with 111 113 known values, or you will certainly end up at a solution that is unphysical. 112 114 113 The returned value is in units of cm^1, on absolute scale.114 115 115 116 NB: The 2nd virial coefficient of the core_shell_parallelepiped is calculated … … 120 121 121 122 For 2d data the orientation of the particle is required, described using 122 angles $\theta$, $\phi$ and $\Psi$ as in the diagrams below. For further 123 details of the calculation and angular dispersions see :ref:`orientation`. 124 The angle $\Psi$ is the rotational angle around the *long_c* axis. For example, 125 $\Psi = 0$ when the *short_b* axis is parallel to the *x*axis of the detector. 123 angles $\theta$, $\phi$ and $\Psi$ as in the diagrams below, for further details 124 of the calculation and angular dispersions see :ref:`orientation` . 125 126 The angle $\Psi$ is the rotational angle around the $C$ axis. 127 For $\theta = 0$ and $\phi = 0$, $\Psi = 0$ corresponds to the $B$ axis 128 oriented parallel to the yaxis of the detector with $A$ along the xaxis. 129 For other $\theta$, $\phi$ values, the parallelepiped has to be first rotated 130 $\theta$ degrees in the $zx$ plane and then $\phi$ degrees around the $z$ axis, 131 before doing a final rotation of $\Psi$ degrees around the resulting $C$ axis 132 of the particle to obtain the final orientation of the parallelepiped. 126 133 127 134 .. note:: For 2d, constraints must be applied during fitting to ensure that the 
sasmodels/models/parallelepiped.py
rb343226 r96153e4 19 19 20 20 The three dimensions of the parallelepiped (strictly here a cuboid) may be 21 given in *any* size order. To avoid multiple fit solutions, especially 22 with MonteCarlo fit methods, it may be advisable to restrict their ranges. 23 There may be a number of closely similar "best fits", so some trial and 24 error, or fixing of some dimensions at expected values, may help. 21 given in *any* size order as long as the particles are randomly oriented (i.e. 22 take on all possible orientations see notes on 2D below). To avoid multiple fit 23 solutions, especially with MonteCarlo fit methods, it may be advisable to 24 restrict their ranges. There may be a number of closely similar "best fits", so 25 some trial and error, or fixing of some dimensions at expected values, may 26 help. 25 27 26 28 The form factor is normalized by the particle volume and the 1D scattering … … 80 82 of the calculation and angular dispersions see :ref:`orientation` . 81 83 82 .. Comment by Miguel Gonzalez:83 The following text has been commented because I think there are two84 mistakes. Psi is the rotational angle around C (but I cannot understand85 what it means against the q plane) and psi=0 corresponds to ax and by.86 87 The angle $\Psi$ is the rotational angle around the $C$ axis against88 the $q$ plane. For example, $\Psi = 0$ when the $B$ axis is parallel89 to the $x$axis of the detector.90 91 84 The angle $\Psi$ is the rotational angle around the $C$ axis. 92 85 For $\theta = 0$ and $\phi = 0$, $\Psi = 0$ corresponds to the $B$ axis … … 97 90 of the particle to obtain the final orientation of the parallelepiped. 98 91 92 .. note:: For 2d, constraints must be applied during fitting to ensure that the 93 inequality $A < B < C$ is not violated, and hence the correct definition 94 of angles is preserved. The calculation will not report an error, 95 but the results may be not correct. 96 99 97 .. _parallelepipedorientation: 100 98
Note: See TracChangeset
for help on using the changeset viewer.