# How can I treat temperature in an input file?

**URL:** <https://openmc.discourse.group/t/how-can-i-treat-temperature-in-an-input-file/21>\
**Category:** User Support\
**Created:** [June 10, 2013, 3:42pm UTC](https://openmc.discourse.group/t/how-can-i-treat-temperature-in-an-input-file/21 "2013-06-10T15:42:42Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![kcd1006](https://avatars.discourse-cdn.com/v4/letter/k/258eb7/32.png) [@kcd1006](https://openmc.discourse.group/u/kcd1006)\
**Post date:** [June 10, 2013, 3:42pm UTC](https://openmc.discourse.group/t/how-can-i-treat-temperature-in-an-input-file/21/1 "2013-06-10T15:42:42Z")

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I tried to find a temperature section in the ‘Writing XML Input Files’ of the OpenMC User’s Guide.  
However, I’ve not found so far.  
I’ve expected that maybe the \<energy\_grid\> element deals with temperature.  
Is it right? If yes, how can I change temperature?  
‘Default:union’ is the only explanation about the \<energy\_grid\>.

Thanks,  
Chidong

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**Author:** ![Adam\_Nelson](https://avatars.discourse-cdn.com/v4/letter/a/8edcca/32.png) [@Adam\_Nelson](https://openmc.discourse.group/u/Adam_Nelson)\
**Post date:** [June 10, 2013, 4:10pm UTC](https://openmc.discourse.group/t/how-can-i-treat-temperature-in-an-input-file/21/2 "2013-06-10T16:10:00Z")

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Hello Chidong,

You are right that there are is no discussion about the temperature of a material in the OpenMC manual; currently the only way to set the temperature is to reference different cross-section data sets (with the \<default\_xs\> element in materials.xml [http://mit-crpg.github.io/openmc/usersguide/input.html#default-xs-element](http://mit-crpg.github.io/openmc/usersguide/input.html#default-xs-element)) and to have consistent number densities. Work is ongoing to incorporate more advanced temperature treatments (and user interaction with these treatments) as discussed here: [https://github.com/mit-crpg/openmc/issues/129](https://github.com/mit-crpg/openmc/issues/129)

Finally, the \<energy\_grid\> element does not affect the temperature of a model; instead it, to a high-level, just changes how the cross-section arrays are allocated and referenced in the computer’s RAM.

Hope this helps,  
Adam