Changes in / [9f12fbe:4050e6a] in sasmodels

Location:

sasmodels/models

Files:

• fractal.c (modified) (2 diffs)
• fractal.py (modified) (4 diffs)

sasmodels/models/fractal.c

@@ -1 +1 @@
 #define INVALID(p) (p.fractal_dim < 0.0)
+
+ static double
+ form_volume(double radius)
+ {
+     return M_4PI_3 * cube(radius);
+ }
 
 static double
@@ -13 +19 @@
 
     //calculate P(q) for the spherical subunits
-    const double V = M_4PI_3*cube(radius);
-    const double pq = V * square((sld_block-sld_solvent)*sas_3j1x_x(q*radius));
+    const double pq = square(form_volume(radius) * (sld_block-sld_solvent)
+                      *sas_3j1x_x(q*radius));
 
     // scale to units cm-1 sr-1 (assuming data on absolute scale)

sasmodels/models/fractal.py

@@ -20 +20 @@
 .. math::
 
-    P(q)&= F(qR_0)^2
-
-    F(q)&= \frac{3 (\sin x - x \cos x)}{x^3}
-
-    V_\text{particle} &= \frac{4}{3}\ \pi R_0
-
+    P(q)&= F(qR_0)^2 \\
+    F(q)&= \frac{3 (\sin x - x \cos x)}{x^3} \\
+    V_\text{particle} &= \frac{4}{3}\ \pi R_0 \\
     S(q) &= 1 + \frac{D_f\  \Gamma\!(D_f-1)}{[1+1/(q \xi)^2\  ]^{(D_f -1)/2}}
     \frac{\sin[(D_f-1) \tan^{-1}(q \xi) ]}{(q R_0)^{D_f}}
@@ -32 +29 @@
 is the fractal dimension, representing the self similarity of the structure. 
 Note that S(q) here goes negative if $D_f$ is too large, and the Gamma function 
-diverges at $D_f$=0 and $D_f$=1.  
+diverges at $D_f=0$ and $D_f=1$.
 
 **Polydispersity on the radius is provided for.**
@@ -47 +44 @@
 ----------
 
-J Teixeira, *J. Appl. Cryst.*, 21 (1988) 781-785
+.. [#] J Teixeira, *J. Appl. Cryst.*, 21 (1988) 781-785
 
-**Author:** NIST IGOR/DANSE **on:** pre 2010
+Authorship and Verification
+----------------------------
 
-**Last Modified by:** Paul Butler **on:** March 20, 2016
-
-**Last Reviewed by:** Paul Butler **on:** March 20, 2016
+* **Author:** NIST IGOR/DANSE **Date:** pre 2010
+* **Converted to sasmodels by:** Paul Butler **Date:** March 19, 2016
+* **Last Modified by:** Paul Butler **Date:** March 12, 2017
+* **Last Reviewed by:** Paul Butler **Date:** March 12, 2017
 
 """
@@ -84 +83 @@
 parameters = [["volfraction", "", 0.05, [0.0, 1], "",
                "volume fraction of blocks"],
-              ["radius",    "Ang",  5.0, [0.0, inf], "",
+              ["radius",    "Ang",  5.0, [0.0, inf], "volume",
                "radius of particles"],
               ["fractal_dim",      "",  2.0, [0.0, 6.0], "",