use old approach by default (temporary)

Base/Types/SimOptions.h

@@ -29,7 +29,7 @@ struct ThreadInfo {
 //! Options to compute mesocrystal formfactors.
 
 struct MesoOptions {
-    bool use_reciprocal_sum{false};
+    bool use_reciprocal_sum{true}; // TODO: change to 'false' in framework of issue #510
     double radius_factor{2.1};
 };