# MMPBSA Polar Energy Calculation Gives nan in polar.xvg

**URL:** <https://gromacs.bioexcel.eu/t/mmpbsa-polar-energy-calculation-gives-nan-in-polar-xvg/11645>\
**Category:** User discussions\
**Created:** [February 27, 2025, 10:39am UTC](https://gromacs.bioexcel.eu/t/mmpbsa-polar-energy-calculation-gives-nan-in-polar-xvg/11645 "2025-02-27T10:39:40Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Suma](https://avatars.discourse-cdn.com/v4/letter/s/22d042/32.png) [@Suma](https://gromacs.bioexcel.eu/u/Suma)\
**Post date:** [February 27, 2025, 10:39am UTC](https://gromacs.bioexcel.eu/t/mmpbsa-polar-energy-calculation-gives-nan-in-polar-xvg/11645/1 "2025-02-27T10:39:40Z")

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I am running an MMPBSA calculation using g\_mmpbsa (VERSION 5.1.2) with GROMACS (VERSION 5.1.2), but I am encountering an issue where the polar solvation energy values are `nan` in `polar.xvg`. The output looks like this:  
@TYPE xy  
@ view 0.15, 0.15, 0.75, 0.85  
@ legend on  
@ legend box on  
@ legend loctype view  
@ legend 0.78, 0.8  
@ legend length 2  
@ s0 legend “Protein PB energy”  
@ s1 legend “8SJZ PB energy”  
@ s2 legend “Protein=8SJZ PB energy”  
80000.000 -10473.799 nan -10406.622  
81000.000 -10706.041 nan -10671.689  
82000.000 -10664.577 nan -10603.726  
Why is the polar solvation energy calculation giving `nan` values?  
Are there specific grid settings, dielectric values, or PB solver parameters I should adjust?  
Could this be due to an issue in the topology file or missing parameters in the system?

I would greatly appreciate any insights, suggestions, or solutions to resolve this issue. If anyone has encountered this problem before and found a fix, please share your approach.

Looking forward to your help.

Best regards,  
Suma