# How to create geometry

**URL:** <https://openmc.discourse.group/t/how-to-create-geometry/3961>\
**Category:** User Support\
**Created:** [February 26, 2024, 5:28pm UTC](https://openmc.discourse.group/t/how-to-create-geometry/3961 "2024-02-26T17:28:00Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![hkumi](https://avatars.discourse-cdn.com/v4/letter/h/85f322/32.png) [@hkumi](https://openmc.discourse.group/u/hkumi)\
**Post date:** [February 26, 2024, 5:28pm UTC](https://openmc.discourse.group/t/how-to-create-geometry/3961/1 "2024-02-26T17:28:00Z")

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Hello everyone,

I just installed OPENMC today. I am very new to this.(basically started today). I have successfully installed openmc. I want to create a simple geometry of a wall but I do not know what to do. I have read the installation guide I do not seems to understand. I have error trying to run even the examples. What should I do?I am using OpenMC 0.14.0. Thanks

“”  
Reading model XML file ‘model.xml’ …  
WARNING: Other XML file input(s) are present. These files may be ignored in  
favor of the model.xml file.  
ERROR: No cross\_sections.xml file was specified in materials.xml or in the  
OPENMC\_CROSS\_SECTIONS environment variable. OpenMC needs such a file to  
identify where to find data libraries. Please consult the user’s guide  
at [https://docs.openmc.org/](https://docs.openmc.org/) for information on how to set up data  
libraries.  
“”

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**Author:** ![M\_Zammataro](https://avatars.discourse-cdn.com/v4/letter/m/46a35a/32.png) [@M\_Zammataro](https://openmc.discourse.group/u/M_Zammataro)\
**Post date:** [February 29, 2024, 8:39am UTC](https://openmc.discourse.group/t/how-to-create-geometry/3961/2 "2024-02-29T08:39:56Z")

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It looks like you need to add the path to your cross\_sections.xml file. You can either use: openmc.config[“cross\_sections”] = “path/to/cross\_sections.xml”  
or  
Materials.cross\_sections = “path/to/cross\_sections.xml”

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<div class="post-metadata">

**Author:** ![hkumi](https://avatars.discourse-cdn.com/v4/letter/h/85f322/32.png) [@hkumi](https://openmc.discourse.group/u/hkumi)\
**Post date:** [February 29, 2024, 8:55am UTC](https://openmc.discourse.group/t/how-to-create-geometry/3961/3 "2024-02-29T08:55:34Z")

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thank you for the response. this solves the problem.