# OpenMC cross\_section.xml problem **URL:** \ **Category:** User Support\ **Created:** [August 15, 2020, 4:53pm UTC](https://openmc.discourse.group/t/openmc-cross-section-xml-problem/698 "2020-08-15T16:53:26Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![huak95](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/huak95/32/1442_2.png) [@huak95](https://openmc.discourse.group/u/huak95)\ **Post date:** [August 15, 2020, 4:53pm UTC](https://openmc.discourse.group/t/openmc-cross-section-xml-problem/698/1 "2020-08-15T16:53:27Z")
Hi there, I’m new in OpenMC and need some help. I using openMC on macOS Catalina install via conda. As tutorial [here](https://docs.openmc.org/en/stable/quickinstall.html) Furthermore I use Jupyter notebook for writing code. Then I tried example \>\> post\_procesing [here](https://docs.openmc.org/en/stable/examples/post-processing.html) I have no issue until ``` ln[9]: plot = openmc.Plot.from_geometry(geometry) plot.pixels = (250, 250) plot.to_ipython_image() ``` **I got this error** ``` Reading settings 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/ for information on how to set up data libraries. ``` But, I already download the file Official Data Libraries [here](https://openmc.org/official-data-libraries/) I download ENDF/B-VII.1 and put it in /Users/saksorn/opt/data/endf Next I set a PATH like this by using vim .zprofile in terminal ![Screen Shot 2563-08-15 at 23.53.12](https://global.discourse-cdn.com/free1/uploads/openmc/original/1X/8d2561a9d61a94c9dbd77cf873b39c71afa8b96b.png) then I try again but it’s have the same error. Moreover when I install OpenMC via conda it dosen’t have a OpenMC in home directory. It install here `/Users/saksorn/opt/miniconda3/envs/openmc-env/lib` I don’t know is that will effect the program or not. Thank you, saksorn. ---
**Author:** ![Pranto](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/pranto/32/489_2.png) [@Pranto](https://openmc.discourse.group/u/Pranto)\ **Post date:** [August 15, 2020, 5:39pm UTC](https://openmc.discourse.group/t/openmc-cross-section-xml-problem/698/2 "2020-08-15T17:39:56Z")
OpenMC cross\_section path variable ```auto export OPENMC_CROSS_SECTIONS='/Users/saksorn/opt/data/endf/cross_sections.xml' export OPENMC_CROSS_SECTIONS ``` > [@huak95](#): > > Moreover when I install OpenMC via conda it dosen’t have a OpenMC in home directory. > It install here > `/Users/saksorn/opt/miniconda3/envs/openmc-env/lib` > I don’t know is that will effect the program or not. It will not affect the program. ---
**Author:** ![huak95](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/huak95/32/1442_2.png) [@huak95](https://openmc.discourse.group/u/huak95)\ **Post date:** [August 16, 2020, 3:48am UTC](https://openmc.discourse.group/t/openmc-cross-section-xml-problem/698/3 "2020-08-16T03:48:03Z")
It’s work fine! Thank you so much, Pranto. It’s will be the same in ubuntu right? ``` export OPENMC_CROSS_SECTIONS='/Users/saksorn/opt/data/endf/cross_sections.xml' export OPENMC_CROSS_SECTIONS ``` ---
**Author:** ![Pranto](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/pranto/32/489_2.png) [@Pranto](https://openmc.discourse.group/u/Pranto)\ **Post date:** [August 16, 2020, 3:55am UTC](https://openmc.discourse.group/t/openmc-cross-section-xml-problem/698/4 "2020-08-16T03:55:52Z")
> [@huak95](#): > > It’s work fine! Glad to hear it. > [@huak95](#): > > It’s will be the same in ubuntu right? Yep. It will be the same also for ubuntu @huak95 ---
**Author:** ![Nilormi](https://avatars.discourse-cdn.com/v4/letter/n/bc8723/32.png) [@Nilormi](https://openmc.discourse.group/u/Nilormi)\ **Post date:** [March 29, 2023, 2:38pm UTC](https://openmc.discourse.group/t/openmc-cross-section-xml-problem/698/5 "2023-03-29T14:38:56Z")
> [@huak95](#): > > ```auto > export OPENMC_CROSS_SECTIONS='/Users/saksorn/opt/data/endf/cross_sections.xml' > export OPENMC_CROSS_SECTIONS > > ``` @Pranto Exactly where shall I type it? It didnot work for me when I typed them inside the openmc-env. ---
**Author:** ![Pranto](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/pranto/32/489_2.png) [@Pranto](https://openmc.discourse.group/u/Pranto)\ **Post date:** [April 10, 2023, 12:52pm UTC](https://openmc.discourse.group/t/openmc-cross-section-xml-problem/698/6 "2023-04-10T12:52:42Z")
@Nilormi If you’re using `bash`, you can add `OPENMC_CROSS_SECTIONS` env variable in your `.bashrc` file. If you’re using `zsh`, then you should write them in your `.zshrc` file instead. Both of these files are typically located in your `home` directory. To know which shell are you using, use the following command: ```bash echo $0 ``` ---
**Author:** ![Nilormi](https://avatars.discourse-cdn.com/v4/letter/n/bc8723/32.png) [@Nilormi](https://openmc.discourse.group/u/Nilormi)\ **Post date:** [April 10, 2023, 3:47pm UTC](https://openmc.discourse.group/t/openmc-cross-section-xml-problem/698/7 "2023-04-10T15:47:09Z")
@Pranto Thank You. But I did resolve this issue already. I am now trying to create geometry .