Merge pull request #2134 from paulromano/thermal-mixed-elastic

Add support for mixed incoherent/coherent elastic thermal scattering

include/openmc/endf.h

@@ -126,6 +126,26 @@ private:
     debye_waller_; //!< Debye-Waller integral divided by atomic mass in [eV^-1]
 };
 
+//==============================================================================
+//! Sum of multiple 1D functions
+//==============================================================================
+
+class Sum1D : public Function1D {
+public:
+  // Constructors
+  explicit Sum1D(hid_t group);
+
+  //! Evaluate each function and sum results
+  //! \param[in] x independent variable
+  //! \return Function evaluated at x
+  double operator()(double E) const override;
+
+  const unique_ptr<Function1D>& functions(int i) const { return functions_[i]; }
+
+private:
+  vector<unique_ptr<Function1D>> functions_; //!< individual functions
+};
+
 //! Read 1D function from HDF5 dataset
 //! \param[in] group HDF5 group containing dataset
 //! \param[in] name Name of dataset

include/openmc/hdf5_interface.h

@@ -61,6 +61,8 @@ void ensure_exists(hid_t obj_id, const char* name, bool attribute = false);
 vector<std::string> group_names(hid_t group_id);
 vector<hsize_t> object_shape(hid_t obj_id);
 std::string object_name(hid_t obj_id);
+hid_t open_object(hid_t group_id, const std::string& name);
+void close_object(hid_t obj_id);
 
 //==============================================================================
 // Fortran compatibility functions

include/openmc/secondary_thermal.h

@@ -150,6 +150,34 @@ private:
                                        //!< each incident energy
 };
 
+//==============================================================================
+//! Mixed coherent/incoherent elastic angle-energy distribution
+//==============================================================================
+
+class MixedElasticAE : public AngleEnergy {
+public:
+  //! Construct from HDF5 file
+  //
+  //! \param[in] group  HDF5 group
+  explicit MixedElasticAE(
+    hid_t group, const CoherentElasticXS& coh_xs, const Function1D& incoh_xs);
+
+  //! Sample distribution for an angle and energy
+  //! \param[in] E_in Incoming energy in [eV]
+  //! \param[out] E_out Outgoing energy in [eV]
+  //! \param[out] mu Outgoing cosine with respect to current direction
+  //! \param[inout] seed Pseudorandom number seed pointer
+  void sample(
+    double E_in, double& E_out, double& mu, uint64_t* seed) const override;
+
+private:
+  CoherentElasticAE coherent_dist_;         //!< Coherent distribution
+  unique_ptr<AngleEnergy> incoherent_dist_; //!< Incoherent distribution
+
+  const CoherentElasticXS& coherent_xs_; //!< Ref. to coherent XS
+  const Function1D& incoherent_xs_;      //!< Polymorphic ref. to incoherent XS
+};
+
 } // namespace openmc
 
 #endif // OPENMC_SECONDARY_THERMAL_H