# Imposing a discontinuity at interface using DG method

**URL:** <https://fenicsproject.discourse.group/t/imposing-a-discontinuity-at-interface-using-dg-method/11780>\
**Category:** dolfinx\
**Created:** [July 19, 2023, 7:40pm UTC](https://fenicsproject.discourse.group/t/imposing-a-discontinuity-at-interface-using-dg-method/11780 "2023-07-19T19:40:17Z")\
**Posts on this page:** 1\
**Showing post:** 21

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**Author:** ![dokken](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/dokken/32/1560_2.png) [@dokken](https://fenicsproject.discourse.group/u/dokken)\
**Post date:** [January 17, 2024, 2:46pm UTC](https://fenicsproject.discourse.group/t/imposing-a-discontinuity-at-interface-using-dg-method/11780/21 "2024-01-17T14:46:35Z")

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I would suggest searching on the forum for your error message, as it is already covered at:

> [@Linear Elasticity Tutorial w/ Quadratic Tetrahedrals](https://fenicsproject.discourse.group/t/linear-elasticity-tutorial-w-quadratic-tetrahedrals/12882/2):
>
> Use dolfinx.io.VTXWriter instead of xdmffile if you are not using isoparametric elements.

and

> [@Cannot write function to XDMF with DG elements](https://fenicsproject.discourse.group/t/cannot-write-function-to-xdmf-with-dg-elements/12442/2):
>
> This is an explicit change to highlight the limitations of the XDMF file format, as in comparison to VTX. In DOLFINx\<0.7.0 any function was interpolated into the function space of the mesh geometry (N-th order Lagrange space, N usually 1). Now you have to interpolate this function into (“CG”, 1) explicitly to save it to xdmf, or use the VTXWriter, which supports arbitrary order “CG”/“DG” elements.

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