# Molecules angle to z axis using gmx gangle

**URL:** https://gromacs.bioexcel.eu/t/molecules-angle-to-z-axis-using-gmx-gangle/3259
**Category:** User discussions
**Created:** [December 7, 2021, 5:48am UTC](https://gromacs.bioexcel.eu/t/molecules-angle-to-z-axis-using-gmx-gangle/3259 "2021-12-07T05:48:15Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![Yogesh](https://avatars.discourse-cdn.com/v4/letter/y/49beb7/32.png) [@Yogesh](https://gromacs.bioexcel.eu/u/Yogesh)
#### Post date: [December 7, 2021, 5:48am UTC](https://gromacs.bioexcel.eu/t/molecules-angle-to-z-axis-using-gmx-gangle/3259/1 "2021-12-07T05:48:16Z")

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Hi all  
I am trying to use Gangle module for calculating angle between molecule and z axis.  
i guess gmx gangle can be used for that. The issue is molecule being symmetrical rotates around its principle axis as well. so i am having trouble defining atoms for vector. looking forward for suggestions from the group.  
I am not very clear about how plane selection works? can i use plane selection for the purpose?

![ztonormal](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/0/08c7ceaab69a9bdde665793cc747ec40a0b21e42.png)

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### Author: ![agustin.zavala](https://avatars.discourse-cdn.com/v4/letter/a/35a633/32.png) [@agustin.zavala](https://gromacs.bioexcel.eu/u/agustin.zavala)
#### Post date: [August 21, 2023, 2:45pm UTC](https://gromacs.bioexcel.eu/t/molecules-angle-to-z-axis-using-gmx-gangle/3259/2 "2023-08-21T14:45:56Z")

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Hello, did you finally solve this issue?