# Function for spatial derivative of the potential field

**URL:** <https://bempp.discourse.group/t/function-for-spatial-derivative-of-the-potential-field/134>\
**Category:** Bempp\
**Created:** [21 April 2022 11:39 UTC](https://bempp.discourse.group/t/function-for-spatial-derivative-of-the-potential-field/134 "2022-04-21T11:39:33Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![mospel](https://avatars.discourse-cdn.com/v4/letter/m/df705f/32.png) [@mospel](https://bempp.discourse.group/u/mospel)\
**Post date:** [21 April 2022 11:39 UTC](https://bempp.discourse.group/t/function-for-spatial-derivative-of-the-potential-field/134/1 "2022-04-21T11:39:33Z")

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Are there functions in BEMPP to calculate the spatial gradient of the potential in a grid function?

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**Author:** ![Elwin](https://yyz2.discourse-cdn.com/free1/user_avatar/bempp.discourse.group/elwin/32/38_2.png) [@Elwin](https://bempp.discourse.group/u/Elwin)\
**Post date:** [29 April 2022 12:39 UTC](https://bempp.discourse.group/t/function-for-spatial-derivative-of-the-potential-field/134/2 "2022-04-29T12:39:52Z")

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At the moment, there is no built-in functionality to calculate the surface gradient of a grid function in bempp-cl.

Notice that the normal gradient of a surface potential is also called the Neumann trace and might be present in the solution vector, depending on the boundary integral formulation.