Added Masses section

src/lammps_structure_writer.cpp

@@ -57,6 +57,13 @@ void LammpsStructureWriter::write_data(const std::string& filename, const size_t
   // END LAMMPS HEADER
 
   // BEGIN LAMMPS BODY
+  file << std::endl;
+  file << "Masses" << std::endl;
+  file << std::endl;
+  for (const auto &t: type) {
+    file << t.second << " " << PeriodicTable::get_mass(t.first) << "    # " << t.first << std::endl;
+  }
+
   file << std::endl;
   file << "Atoms # atomic" << std::endl;
   file << std::endl;