# 3D periodic boundary condition

**URL:** <https://community.freefem.org/t/3d-periodic-boundary-condition/2093>\
**Category:** General Discussion\
**Created:** [October 28, 2022, 2:42pm UTC](https://community.freefem.org/t/3d-periodic-boundary-condition/2093 "2022-10-28T14:42:05Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![danmo](https://avatars.discourse-cdn.com/v4/letter/d/ea666f/32.png) [@danmo](https://community.freefem.org/u/danmo)\
**Post date:** [October 28, 2022, 2:42pm UTC](https://community.freefem.org/t/3d-periodic-boundary-condition/2093/1 "2022-10-28T14:42:05Z")

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Hi all,

I want to apply 3-D periodic BC on a structure, but when running the code, I encounter the following error:

Exec error : periodic: Sorry one vertex of face is losted

Does anyone know what could be the reason for this error?

Thank you !

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**Author:** ![Alexandru](https://avatars.discourse-cdn.com/v4/letter/a/e19b73/32.png) [@Alexandru](https://community.freefem.org/u/Alexandru)\
**Post date:** [October 28, 2022, 3:03pm UTC](https://community.freefem.org/t/3d-periodic-boundary-condition/2093/2 "2022-10-28T15:03:29Z")

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Hi Daniel, Meshes on opposite faces are identical ?

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**Author:** ![danmo](https://avatars.discourse-cdn.com/v4/letter/d/ea666f/32.png) [@danmo](https://community.freefem.org/u/danmo)\
**Post date:** [October 31, 2022, 11:07am UTC](https://community.freefem.org/t/3d-periodic-boundary-condition/2093/3 "2022-10-31T11:07:07Z")

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Hi,  
Thank you for your tip. I guess that was the issue !