diff --git a/include/openmc/dagmc.h b/include/openmc/dagmc.h
index 51d97d737..052e53d51 100644
--- a/include/openmc/dagmc.h
+++ b/include/openmc/dagmc.h
@@ -26,15 +26,10 @@ extern moab::DagMC* DAG;
 
 extern "C" void load_dagmc_geometry();
 extern "C" void free_memory_dagmc();
-
+extern "C" pugi::xml_document* read_uwuw_materials();
+std::string get_uwuw_materials_xml();
 } // namespace openmc
 
 #endif // DAGMC
 
 #endif // OPENMC_DAGMC_H
-
-#ifdef DAGMC
-extern "C" constexpr bool dagmc_enabled = true;
-#else
-extern "C" constexpr bool dagmc_enabled = false;
-#endif
diff --git a/include/openmc/settings.h b/include/openmc/settings.h
index e95bcb107..c44c8edb1 100644
--- a/include/openmc/settings.h
+++ b/include/openmc/settings.h
@@ -16,6 +16,8 @@
 
 namespace openmc {
 
+extern "C" bool dagmc_enabled;
+
 //==============================================================================
 // Global variable declarations
 //==============================================================================
diff --git a/src/cross_sections.cpp b/src/cross_sections.cpp
index ed963b23f..5c2e7cb50 100644
--- a/src/cross_sections.cpp
+++ b/src/cross_sections.cpp
@@ -2,6 +2,9 @@
 
 #include "openmc/constants.h"
 #include "openmc/container_util.h"
+#ifdef DAGMC
+#include "openmc/dagmc.h"
+#endif
 #include "openmc/error.h"
 #include "openmc/file_utils.h"
 #include "openmc/settings.h"
@@ -81,14 +84,27 @@ extern "C" void read_mg_cross_sections_header();
 
 void read_cross_sections_xml()
 {
-  // Check if materials.xml exists
+  pugi::xml_document doc;
   std::string filename = settings::path_input + "materials.xml";
-  if (!file_exists(filename)) {
-    fatal_error("Material XML file '" + filename + "' does not exist.");
+#ifdef DAGMC
+  std::string s;
+  if (settings::dagmc) {
+    s = get_uwuw_materials_xml();
   }
 
+  if(s != "") {
+    doc.load_file(s.c_str());
+  } else {
+#endif
+    // Check if materials.xml exists
+    if (!file_exists(filename)) {
+      fatal_error("Material XML file '" + filename + "' does not exist.");
+    }
+
+#ifdef DAGMC
+  }
+#endif
   // Parse materials.xml file
-  pugi::xml_document doc;
   doc.load_file(filename.c_str());
   auto root = doc.document_element();
 
diff --git a/src/dagmc.cpp b/src/dagmc.cpp
index bc3362892..cb0ce476f 100644
--- a/src/dagmc.cpp
+++ b/src/dagmc.cpp
@@ -12,6 +12,16 @@
 #include <algorithm>
 #include <fstream>
 
+namespace openmc {
+
+#ifdef DAGMC
+bool dagmc_enabled = true;
+#else
+bool dagmc_enabled = false;
+#endif
+
+}
+
 #ifdef DAGMC
 
 #include "uwuw.hpp"
@@ -27,20 +37,53 @@ moab::DagMC* DAG;
 
 } // namespace model
 
-bool write_materials_xml(UWUW uwuw) {
-  // if there is a material library in the file,
-  // write a material.xml file
-  std::ofstream mats_xml("materials.xml");
-  // write header
-  mats_xml << "<?xml version=\"1.0\"?>\n";
-  mats_xml << "<materials>\n";
-  std::map<std::string, pyne::Material> ml = uwuw.material_library;
-  std::map<std::string, pyne::Material>::iterator it;
-  // write materials
-  for (it = ml.begin(); it != ml.end(); it++) { mats_xml << it->second.openmc("atom");  }
-  // write footer
-  mats_xml << "</materials>";
-  mats_xml.close();
+
+std::string get_uwuw_materials_xml() {
+  UWUW uwuw(DAGMC_FILENAME);
+
+  std::stringstream ss;
+  if (uwuw.material_library.size() != 0) {
+    // write header
+    ss << "<?xml version=\"1.0\"?>\n";
+    ss << "<materials>\n";
+    std::map<std::string, pyne::Material> ml = uwuw.material_library;
+    std::map<std::string, pyne::Material>::iterator it;
+    // write materials
+    for (it = ml.begin(); it != ml.end(); it++) {
+      ss << it->second.openmc("atom");
+    }
+    // write footer
+    ss << "</materials>";
+  }
+
+  return ss.str();
+}
+
+pugi::xml_document* read_uwuw_materials() {
+  pugi::xml_document* doc = NULL;
+
+  std::string ss = get_uwuw_materials_xml();
+  if(ss != "") {
+    doc = new pugi::xml_document();
+    pugi::xml_parse_result result = doc->load_string(ss.c_str());
+  }
+
+  return doc;
+}
+
+bool write_uwuw_materials_xml() {
+  bool found_mats;
+  std::string ss = get_uwuw_materials_xml();
+    // if there is a material library in the file
+  if (ss != "") {
+    // write a material.xml file
+    std::ofstream mats_xml("materials.xml");
+    mats_xml << get_uwuw_materials_xml();
+    mats_xml.close();
+    found_mats = true;
+  }
+
+  return found_mats;
 }
 
 void load_dagmc_geometry()
@@ -63,7 +106,7 @@ void load_dagmc_geometry()
         err_msg << "A materials.xml file is present along with UWUW material definitions";
         fatal_error(err_msg.str());
       }
-    write_materials_xml(uwuw);
+    //    write_materials_xml(uwuw);
   }
 
   int32_t dagmc_univ_id = 0; // universe is always 0 for DAGMC runs
@@ -78,14 +121,14 @@ void load_dagmc_geometry()
   if (using_uwuw) {
     DMD.load_property_data();
   }
-  
+
   std::vector<std::string> keywords;
   keywords.push_back("mat");
   keywords.push_back("density");
   keywords.push_back("boundary");
   std::map<std::string, std::string> dum;
   rval = model::DAG->parse_properties(keywords, dum, ":/");
-  
+
   // initialize cell objects
   model::n_cells = model::DAG->num_entities(3);
 
@@ -174,8 +217,8 @@ void load_dagmc_geometry()
     if (model::DAG->has_prop(surf_handle, "boundary")) {
       rval = model::DAG->prop_value(surf_handle, "boundary", bc_value);
       MB_CHK_ERR_CONT(rval);
-      to_lower(bc_value);    
-    
+      to_lower(bc_value);
+
       if (bc_value == "transmit" || bc_value == "transmission") {
         s->bc_ = BC_TRANSMIT;
       } else if (bc_value == "vacuum") {
@@ -207,5 +250,6 @@ void free_memory_dagmc()
   delete model::DAG;
 }
 
+
 }
 #endif
diff --git a/src/dagmc_header.F90 b/src/dagmc_header.F90
index 9895791ac..4a97f7f0c 100644
--- a/src/dagmc_header.F90
+++ b/src/dagmc_header.F90
@@ -13,6 +13,11 @@ module dagmc_header
     subroutine free_memory_dagmc() bind(C)
     end subroutine free_memory_dagmc
 
+    function read_uwuw_materials() result(doc) bind(C)
+      import C_PTR
+      type(C_PTR) :: doc
+    end function read_uwuw_materials
+
   end interface
 
 end module dagmc_header
diff --git a/src/input_xml.F90 b/src/input_xml.F90
index c497c79b9..496f42f76 100644
--- a/src/input_xml.F90
+++ b/src/input_xml.F90
@@ -520,18 +520,30 @@ contains
     ! Display output message
     call write_message("Reading materials XML file...", 5)
 
+#ifdef DAGMC
+    if (dagmc) then
+       doc % ptr = read_uwuw_materials()
+    end if
+
+    if (.not. c_associated(doc % ptr)) then
+#endif
+
     ! Check if materials.xml exists
     filename = trim(path_input) // "materials.xml"
     inquire(FILE=filename, EXIST=file_exists)
     if (.not. file_exists) then
       call fatal_error("Material XML file '" // trim(filename) // "' does not &
            &exist!")
-    end if
+   end if
 
     ! Parse materials.xml file
     call doc % load_file(filename)
-    root = doc % document_element()
 
+#ifdef DAGMC
+    end if
+#endif
+
+    root = doc % document_element()
     call read_materials(root % ptr)
 
     ! Get pointer to list of XML <material>