Changeset c915373 in sasmodels

Timestamp:

Aug 1, 2016 7:35:19 PM (8 years ago)

Author:

Paul Kienzle <pkienzle@…>

Branches:

master, core_shell_microgels, costrafo411, magnetic_model, release_v0.94, release_v0.95, ticket-1257-vesicle-product, ticket_1156, ticket_1265_superball, ticket_822_more_unit_tests

Children:

33875e3

Parents:

ec77322

Message:

polymer micelle: improve accuracy of kernel for low q

File:

• sasmodels/models/polymer_micelle_kernel.c (modified) (1 diff)

sasmodels/models/polymer_micelle_kernel.c

@@ -36 +36 @@
     // Self-correlation term of the chains
     const double qrg2 = q*radius_gyr*q*radius_gyr;
-    const double debye_chain = (qrg2 == 0.0) ? 1.0 : 2.0*(exp(-qrg2)-1+qrg2)/(qrg2*qrg2);
+    const double debye_chain = (qrg2 == 0.0) ? 1.0 : 2.0*(expm1(-qrg2)+qrg2)/(qrg2*qrg2);
     const double term2 = n_aggreg * beta_corona * beta_corona * debye_chain;
 
     // Interference cross-term between core and chains
-    const double chain_ampl = (qrg2 == 0.0) ? 1.0 : (1-exp(-qrg2))/qrg2;
+    const double chain_ampl = (qrg2 == 0.0) ? 1.0 : -expm1(-qrg2)/qrg2;
     const double bes_corona = sinc(q*(radius_core + d_penetration * radius_gyr));
     const double term3 = 2 * n_aggreg * n_aggreg * beta_core * beta_corona *