# Nested hexagonal lattice.

**URL:** <https://openmc.discourse.group/t/nested-hexagonal-lattice/357>\
**Category:** User Support\
**Created:** [October 2, 2018, 6:13pm UTC](https://openmc.discourse.group/t/nested-hexagonal-lattice/357 "2018-10-02T18:13:44Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Vedha](https://avatars.discourse-cdn.com/v4/letter/v/6bbea6/32.png) [@Vedha](https://openmc.discourse.group/u/Vedha)\
**Post date:** [October 2, 2018, 6:13pm UTC](https://openmc.discourse.group/t/nested-hexagonal-lattice/357/1 "2018-10-02T18:13:44Z")

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Hi Paul,

I want to create a geometry model with nested hexagonal lattice, such as, a pin lattice inside a hexagonal subassembly lattice inside a core. There is a condition that I read in manual that states “The \<hex\_lattice\> can be used to represent repeating structures (e.g. fuel pins in an assembly) or other geometry which naturally fits onto a hexagonal grid or hexagonal prism grid. Each cell within the lattice is filled with a specified universe. This lattice uses the “flat-topped hexagon” scheme where **two of the six edges are perpendicular to the y-axis**.”

In case of nested hexgonal lattice models, if one lattice has 2 edges perpendicular to y-axis then the other lattice must have 2 edges perpendicular to x-axis, as I understand it.

So, is there a way to change the orientation of hexlattice such that 2 edges are perpendicular to the x-axis?

Thanks!

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**Author:** ![paulromano](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/paulromano/32/486_2.png) [@paulromano](https://openmc.discourse.group/u/paulromano)\
**Post date:** [October 2, 2018, 2:05pm UTC](https://openmc.discourse.group/t/nested-hexagonal-lattice/357/2 "2018-10-02T14:05:20Z")

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Yes, what you would need to do is insert an extra universe that contains a single cell rotated by 30 degrees. Check out this notebook for an example where this is done:  
[https://github.com/paulromano/cnl-workshop/blob/master/notebooks/05-lattices/Solution/Lattices-Solution.ipynb](https://github.com/paulromano/cnl-workshop/blob/master/notebooks/05-lattices/Solution/Lattices-Solution.ipynb)

Best regards,  
Paul

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**Author:** ![Vedha](https://avatars.discourse-cdn.com/v4/letter/v/6bbea6/32.png) [@Vedha](https://openmc.discourse.group/u/Vedha)\
**Post date:** [October 3, 2018, 5:03am UTC](https://openmc.discourse.group/t/nested-hexagonal-lattice/357/3 "2018-10-03T05:03:58Z")

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It worked!! Thanks, Paul!