# Geometry xml file fail **URL:** \ **Category:** User Support\ **Created:** [April 18, 2024, 9:18am UTC](https://openmc.discourse.group/t/geometry-xml-file-fail/4174 "2024-04-18T09:18:22Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![gglamzn](https://avatars.discourse-cdn.com/v4/letter/g/e19adc/32.png) [@gglamzn](https://openmc.discourse.group/u/gglamzn)\ **Post date:** [April 18, 2024, 9:18am UTC](https://openmc.discourse.group/t/geometry-xml-file-fail/4174/1 "2024-04-18T09:18:22Z")
Hi , I want to undergo OPENMC simulations from .step files such as Catia. First I did a fuction in order to convert my .step file , using cad\_to\_dagmc The code: #Libraries import cadquery as cq from cad\_to\_dagmc import CadToDagmc import os import openmc def step\_to\_openmc\_h5m(input\_step\_file\_path: str, output\_file\_name: str, output\_dir: str) → str: “”"Converts a STEP file to a DAGMC h5m file usable for simulations on OpenMC. ```auto Args: input_step_file_path (str): The path to the input STEP file. output_file_name (str): The desired name of the output h5m file. output_dir (str): The directory where the output h5m file will be saved. Returns: str: The path to the generated h5m file. """ try: converter = CadToDagmc()# Initialize CadToDagmc instance # Add the STEP file to the converter converter.add_stp_file(input_step_file_path,material_tags=["mat_air"]) #fill the geometry with a defined material # Generate the output h5m file path output_h5m_file_path = os.path.join(output_dir, output_file_name) # Export the DAGMC h5m file converter.export_dagmc_h5m_file(filename=output_h5m_file_path) return output_h5m_file_path except Exception as e: print(f"Error occurred while converting the STEP file: {e}") return "" ``` I tried with a basic .step file and It’s successfull Then i want to do a simple simulation but first I have to get my xml file with all the parameters : def create\_simulation\_file(h5m\_file\_path,output\_directory): ``` # Define the number of particles n_particles = 1000 # Create settings for neutron simulation my_neutron_settings = openmc.Settings() my_neutron_settings.run_mode = "fixed source" my_neutron_settings.particles = n_particles my_neutron_settings.batches = 10 my_neutron_settings.photon_transport = False # Create a neutron source my_source = openmc.IndependentSource() my_source.space = openmc.stats.Point((0, 0, 0)) my_source.angle = openmc.stats.Isotropic() my_source.energy = openmc.stats.Discrete([14.06e6], [1]) my_source.particle = "neutron" # Assign the source to settings my_neutron_settings.source = my_source # Create tallies for neutron flux tally = openmc.Tally() tally.scores = ['flux'] tallies = openmc.Tallies([tally]) # Create materials mat_air = openmc.Material(name="Air") mat_air.add_element("N", 0.784431) mat_air.add_element("O", 0.210748) mat_air.add_element("Ar", 0.0046) mat_air.set_density("g/cc", 0.001205) materials = openmc.Materials([mat_air]) # Create geometry with h5m file geometry = openmc.Geometry() geometry.file = h5m_file_path # Create an OpenMC Model model = openmc.model.Model(geometry=geometry, materials=materials, settings=my_neutron_settings, tallies=tallies) model.export_to_model_xml(output_directory) ``` this xml file is aimed to umdergo the simulation in an another function. I unfortunately get this error , compiling create\_simulation\_file : AttributeError Traceback (most recent call last) Cell In[15], line 50 48 # Export the model to XML 49 output\_directory =“/home/gauthier/Stage/Catia/” —\> 50 model.export\_to\_model\_xml(output\_directory) File ~/miniforge3/envs/openmc-env/lib/python3.12/site-packages/openmc/model/model.py:506, in Model.export\_to\_model\_xml(self, path, remove\_surfs) 504 mesh\_memo = set() 505 settings\_element = self.settings.to\_xml\_element(mesh\_memo) → 506 geometry\_element = self.geometry.to\_xml\_element() 508 xml.clean\_indentation(geometry\_element, level=1) 509 xml.clean\_indentation(settings\_element, level=1) File ~/miniforge3/envs/openmc-env/lib/python3.12/site-packages/openmc/geometry.py:137, in Geometry.to\_xml\_element(self, remove\_surfs) 135 # Create XML representation 136 element = ET.Element(“geometry”) → 137 self.root\_universe.create\_xml\_subelement(element, memo=set()) 139 # Sort the elements in the file 140 element[:] = sorted(element, key=lambda x: ( 141 x.tag, int(x.get(‘id’)))) AttributeError: ‘NoneType’ object has no attribute ‘create\_xml\_subelement’ and I dont really know how to fix it. Does somebody knows why it does this? Best regards. ---
**Author:** ![Shimwell](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/shimwell/32/3876_2.png) [@Shimwell](https://openmc.discourse.group/u/Shimwell)\ **Post date:** [April 19, 2024, 8:15am UTC](https://openmc.discourse.group/t/geometry-xml-file-fail/4174/2 "2024-04-19T08:15:08Z")
Great to see [cad-to-dagmc](https://github.com/fusion-energy/cad_to_dagmc) is working for you. I think the issue here is that the way you are loading the dagmc file into openmc. This part looks like the error ```auto geometry = openmc.Geometry() geometry.file = h5m_file_path ``` Try this instead, I grabbed it from the neutronics-workshop repo. ```auto bound_dag_univ = openmc.DAGMCUniverse(filename='dagmc.h5m').bounded_universe() geometry = openmc.Geometry(root=bound_dag_univ) ``` By the way i hope to update the cad based neutronics examples in the [neutronics workshop](https://github.com/fusion-energy/neutronics-workshop/tree/main/tasks) soon