# Unreasonable umbrella potential plot

**URL:** <https://gromacs.bioexcel.eu/t/unreasonable-umbrella-potential-plot/4180>\
**Category:** User discussions\
**Tags:** umbrella-sampling\
**Created:** [May 17, 2022, 3:14am UTC](https://gromacs.bioexcel.eu/t/unreasonable-umbrella-potential-plot/4180 "2022-05-17T03:14:46Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Maleesha97](https://avatars.discourse-cdn.com/v4/letter/m/f07891/32.png) [@Maleesha97](https://gromacs.bioexcel.eu/u/Maleesha97)\
**Post date:** [May 17, 2022, 3:14am UTC](https://gromacs.bioexcel.eu/t/unreasonable-umbrella-potential-plot/4180/1 "2022-05-17T03:14:46Z")

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GROMACS version: version 2021.5  
GROMACS modification: Yes/No  
Here post your question  
Hello Gromacs users,

I’m a beginner computational chemistry student using Gromcs for my undergraduate research. I capped a 3 nm Silver nanoparticle with amino acid ; ARG and carried out umbrella sampling by pulling one amino acid residue away from the nanoparticle. I followed the umbrella sampling tutorial designed by @jalemkul . However when I used wham, I get a quite odd looking plot for umbrella potential. Also I get 2 warnings : WARNING, no data point in bin 14 (z=0.510967) !  
You may not get a reasonable profile. Check your histograms!

WARNING, no data point in bin 57 (z=1.64511) !  
You may not get a reasonable profile. Check your histograms!

Here’s the histogram and the umbrella potential plot.

 ![Histogram](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/2/222529e34c6b64f5d7d664bd12187d803fe1535f.png)  
 ![Umbrella potential](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/d/d340fe4bba6a687752ea55fca6bc4ea4c5c44bdd.png)

If anyone could tell me where it has gone wrong or the possible reason for the unreasonable plot it would be of great help. Thank you in advance.

Regards,  
Maleesha

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**Author:** ![dmorozov](https://avatars.discourse-cdn.com/v4/letter/d/dec6dc/32.png) [@dmorozov](https://gromacs.bioexcel.eu/u/dmorozov)\
**Post date:** [May 22, 2022, 8:09am UTC](https://gromacs.bioexcel.eu/t/unreasonable-umbrella-potential-plot/4180/2 "2022-05-22T08:09:11Z")

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try to reduce number of bins, with `gmx wham -bins` option. By default there is 200 bins, reduce it to lets say 50 first. But in general you need to simulate more umbrella windows. for example in you figures there is a gap between umbrella #5 and #6, which causes energy jump at ~1.65 nm in PMF, also there is definitely a problem with umbrella at ~3.6 nm.

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**Author:** ![Maleesha97](https://avatars.discourse-cdn.com/v4/letter/m/f07891/32.png) [@Maleesha97](https://gromacs.bioexcel.eu/u/Maleesha97)\
**Post date:** [July 5, 2022, 7:28pm UTC](https://gromacs.bioexcel.eu/t/unreasonable-umbrella-potential-plot/4180/3 "2022-07-05T19:28:17Z")

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My apologies for not responding soon. Thank you so much for your suggestions. I also found an error in my mdp file and I’m going to increse the number of sampling windows as you have suggested. Thank you for your kindness.

Maleesha.