# Issue Importing XDMF Mesh in FESTIM **URL:** \ **Category:** User Support\ **Created:** [September 26, 2025, 2:45pm UTC](https://festim.discourse.group/t/issue-importing-xdmf-mesh-in-festim/144 "2025-09-26T14:45:44Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Andrea](https://avatars.discourse-cdn.com/v4/letter/a/c37758/32.png) [@Andrea](https://festim.discourse.group/u/Andrea)\ **Post date:** [September 26, 2025, 2:45pm UTC](https://festim.discourse.group/t/issue-importing-xdmf-mesh-in-festim/144/1 "2025-09-26T14:45:44Z")
Hello, I generated a 2D mesh for my case study (1 cm Tungsten, 3 cm EUROFER, and 2 cm FLiBe) using DolfinX and exported it into two files: `mesh_domains.xdmf` and `mesh_boundaries.xdmf`. Here is the code I used to load the mesh in FESTIM: import festim as F import numpy as np my\_model = F.Simulation() my\_model.mesh = F.MeshFromXDMF(volume\_file=“mesh\_domains.xdmf”, boundary\_file=“mesh\_boundaries.xdmf”) However, I get the following error: \*\*\* Error: Unable to open XDMF file. \*\*\* Reason: XDMF file “mesh\_domains.xdmf” does not exist. \*\*\* Where: This error was encountered inside XDMFFile.cpp. \*\*\* Process: 0 * * * \*\*\* DOLFIN version: 2019.1.0 \*\*\* Git changeset: ec7503cef5f328d4927ba1050abe55c3519ac4e9 \*\*\* ------------------------------------------------------------------------- ERROR conda.cli.main\_run:execute(127): `conda run python /home/ndrea_i_aio/festim/TESI/MODEL_W_EURO_FLiBe` failed. (See above for error) I have confirmed that the files exist in my `TESI` directory. Could you please advise how to correctly import XDMF meshes into FESTIM, or suggest what might be causing this error? Thank you very much for your help. Best regards, Andrea ---
**Author:** ![remidm](https://yyz2.discourse-cdn.com/free1/user_avatar/festim.discourse.group/remidm/32/4_2.png) [@remidm](https://festim.discourse.group/u/remidm)\ **Post date:** [September 26, 2025, 6:05pm UTC](https://festim.discourse.group/t/issue-importing-xdmf-mesh-in-festim/144/2 "2025-09-26T18:05:04Z")
> [@Andrea](#): > > \*\*\* Reason: XDMF file “mesh\_domains.xdmf” does not exist. Hi @Andrea! this error message indicates that the file `mesh_domains.xdmf` isn’t found by your script. The path that is passed to `volume_file` needs to be the relative path from where you execute your script. ---
**Author:** ![Andrea](https://avatars.discourse-cdn.com/v4/letter/a/c37758/32.png) [@Andrea](https://festim.discourse.group/u/Andrea)\ **Post date:** [September 26, 2025, 7:58pm UTC](https://festim.discourse.group/t/issue-importing-xdmf-mesh-in-festim/144/3 "2025-09-26T19:58:24Z")
Thanks for the quick answer. I have now fixed the paths and they are correct. However, I am still facing an issue when importing the mesh. This is the error I get: ```auto File "/home/ndrea_i_aio/festim/TESI/MODEL_W_EURO_FLiBe", line 6, in my_model.mesh = F.MeshFromXDMF(volume_file="/home/ndrea_i_aio/festim/TESI/mesh_domains.xdmf", boundary_file="/home/ndrea_i_aio/festim/TESI/mesh_boundaries.xdmf") ~~~~~~~~~~~~~~ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/home/ndrea_i_aio/miniconda3/envs/festim_env_2/lib/python3.13/site-packages/festim/meshing/mesh_from_xdmf.py", line 28, in __init__ self.define_markers() ~~~~~~~~~~~~~~~~~~~ ^^ File "/home/ndrea_i_aio/miniconda3/envs/festim_env_2/lib/python3.13/site-packages/festim/meshing/mesh_from_xdmf.py", line 43, in define_markers f.XDMFFile(self.boundary_file).read(surface_markers, "f") ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^^^^^^^^^^^^^^^^^^^^^^ RuntimeError: *** ------------------------------------------------------------------------- *** DOLFIN encountered an error. If you are not able to resolve this issue *** using the information listed below, you can ask for help at *** *** fenics-support@googlegroups.com *** *** Remember to include the error message listed below and, if possible, *** include a *minimal* running example to reproduce the error. *** *** ------------------------------------------------------------------------- *** Error: Unable to recognise cell type. *** Reason: Unknown value "". *** Where: This error was encountered inside XDMFFile.cpp. *** Process: 0 *** *** DOLFIN version: 2019.1.0 *** Git changeset: ec7503cef5f328d4927ba1050abe55c3519ac4e9 *** ------------------------------------------------------------------------- ERROR conda.cli.main_run:execute(127): `conda run python /home/ndrea_i_aio/festim/TESI/MODEL_W_EURO_FLiBe` failed. (See above for error) ``` Could this error be due to an incompatibility between FESTIM (Fenics 2019) and DolfinX? I am also including the code I use to generate the mesh: ```auto import numpy as np import gmsh from mpi4py import MPI import os from dolfinx.io import gmshio import matplotlib.pyplot as plt import pyvista from dolfinx import plot # Geometry wi_tun = 1e-2 # tungsten thickness wi_euro = 3e-2 # EUROFER thickness wi_FLiBe = 2e-2 # FLiBe thickness Le = 1 def create_three_region_mesh(): width_tung = wi_tun width_euro = wi_euro width_FLiBe = wi_FLiBe length = Le gmsh.initialize() gmsh.model.add("three_regions") # Points p1 = gmsh.model.geo.addPoint(0, 0, 0) p2 = gmsh.model.geo.addPoint(width_tung, 0, 0) p3 = gmsh.model.geo.addPoint(0, length, 0) p4 = gmsh.model.geo.addPoint(width_tung, length, 0) p5 = gmsh.model.geo.addPoint(width_tung + width_euro, 0, 0) p6 = gmsh.model.geo.addPoint(width_tung + width_euro, length, 0) p7 = gmsh.model.geo.addPoint(width_tung + width_euro + width_FLiBe, 0, 0) p8 = gmsh.model.geo.addPoint(width_tung + width_euro + width_FLiBe, length, 0) # Lines Tungsten l1 = gmsh.model.geo.addLine(p1, p2) l2 = gmsh.model.geo.addLine(p3, p1) l3 = gmsh.model.geo.addLine(p4, p3) l4 = gmsh.model.geo.addLine(p2, p4) # Lines EUROFER l5 = gmsh.model.geo.addLine(p2, p5) l6 = gmsh.model.geo.addLine(p5, p6) l7 = gmsh.model.geo.addLine(p6, p4) # Lines FLiBe l8 = gmsh.model.geo.addLine(p5, p7) l9 = gmsh.model.geo.addLine(p7, p8) l10 = gmsh.model.geo.addLine(p8, p6) l11 = gmsh.model.geo.addLine(p6, p5) # Curve Loops tung_loop = gmsh.model.geo.addCurveLoop([l1, l4, l3, l2]) euro_loop = gmsh.model.geo.addCurveLoop([l5, l6, l7, -l4]) flibe_loop = gmsh.model.geo.addCurveLoop([l8, l9, l10, l11]) # Surfaces tung_surf = gmsh.model.geo.addPlaneSurface([tung_loop]) euro_surf = gmsh.model.geo.addPlaneSurface([euro_loop]) flibe_surf = gmsh.model.geo.addPlaneSurface([flibe_loop]) gmsh.model.geo.synchronize() # Mesh size gmsh.option.setNumber("Mesh.MeshSizeMin", 0.02) gmsh.option.setNumber("Mesh.MeshSizeMax", 0.02) # Physical groups gmsh.model.addPhysicalGroup(2, [tung_surf], 1) gmsh.model.setPhysicalName(2, 1, "Tungsten") gmsh.model.addPhysicalGroup(2, [euro_surf], 2) gmsh.model.setPhysicalName(2, 2, "EuroFer") gmsh.model.addPhysicalGroup(2, [flibe_surf], 3) gmsh.model.setPhysicalName(2, 3, "FLiBe") gmsh.model.addPhysicalGroup(1, [l2], 4) # Left gmsh.model.addPhysicalGroup(1, [l9], 5) # Right gmsh.model.addPhysicalGroup(1, [l3, l7, l10], 6) # Top gmsh.model.addPhysicalGroup(1, [l1, l5, l8], 7) # Bottom gmsh.model.addPhysicalGroup(1, [l4], 8) # Interface W-Euro gmsh.model.addPhysicalGroup(1, [l11], 9) # Interface Euro-FLiBe gmsh.model.mesh.generate(2) # Conversion to dolfinx mesh_2d, cell_tags, facet_tags = gmshio.model_to_mesh( gmsh.model, MPI.COMM_WORLD, 0, gdim=2 ) gmsh.finalize() total_width = width_tung + width_euro + width_FLiBe return mesh_2d, total_width, width_tung, width_euro, width_FLiBe, cell_tags, facet_tags mesh_2d, total_width, width_tung, width_euro, width_FLiBe, cell_tags, facet_tags = create_three_region_mesh() # Export from dolfinx.io import XDMFFile output_dir = "TESI" os.makedirs(output_dir, exist_ok=True) domains_file = os.path.join(output_dir, "mesh_domains.xdmf") with XDMFFile(MPI.COMM_WORLD, domains_file, "w") as xdmf: xdmf.write_mesh(mesh_2d) xdmf.write_meshtags(cell_tags, mesh_2d.geometry, geometry_xpath="/Mesh/Geometry") boundaries_file = os.path.join(output_dir, "mesh_boundaries.xdmf") with XDMFFile(MPI.COMM_WORLD, boundaries_file, "w") as xdmf: xdmf.write_mesh(mesh_2d) xdmf.write_meshtags(facet_tags, mesh_2d.geometry, geometry_xpath="/Mesh/Geometry") ``` Thanks in advance! ---
**Author:** ![remidm](https://yyz2.discourse-cdn.com/free1/user_avatar/festim.discourse.group/remidm/32/4_2.png) [@remidm](https://festim.discourse.group/u/remidm)\ **Post date:** [September 29, 2025, 12:39pm UTC](https://festim.discourse.group/t/issue-importing-xdmf-mesh-in-festim/144/4 "2025-09-29T12:39:15Z")
I don’t think mixing FESTIM1 and dolfinx is a good idea. You may want to use FESTIM2 - which relies on dolfinx. Our FESTIM2 tutorial is building up [here](https://festim-workshop.readthedocs.io/en/festim2/intro.html) ---
**Author:** ![Andrea](https://avatars.discourse-cdn.com/v4/letter/a/c37758/32.png) [@Andrea](https://festim.discourse.group/u/Andrea)\ **Post date:** [September 30, 2025, 5:24pm UTC](https://festim.discourse.group/t/issue-importing-xdmf-mesh-in-festim/144/5 "2025-09-30T17:24:27Z")
Got it, thanks for the clarification! Sorry for the trouble. I’ll use FESTIM1 with SALOME.