# Particle 151 had a negative distance to a lattice boundary

**URL:** <https://openmc.discourse.group/t/particle-151-had-a-negative-distance-to-a-lattice-boundary/4596>\
**Category:** User Support\
**Created:** [July 22, 2024, 2:30am UTC](https://openmc.discourse.group/t/particle-151-had-a-negative-distance-to-a-lattice-boundary/4596 "2024-07-22T02:30:05Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![cro](https://avatars.discourse-cdn.com/v4/letter/c/e5b9ba/32.png) [@cro](https://openmc.discourse.group/u/cro)\
**Post date:** [July 22, 2024, 2:30am UTC](https://openmc.discourse.group/t/particle-151-had-a-negative-distance-to-a-lattice-boundary/4596/1 "2024-07-22T02:30:05Z")

</div>

hello everyone! Hope everything goes smoothly!  
I am a beginner in OpenMC. I defined a lattice material in a sphere and set up a fixed source.  
**Edit:** I suspect there may be an issue with the settings of the source. What I want is for the source to function as a disk, with the disk surface parallel to the lattice surface, as shown in the diagram,

 ![20240722105213](https://global.discourse-cdn.com/free1/uploads/openmc/original/2X/d/d1e6a95cafd9c42ea8e0ea059b96c2d158b42e16.png)

But I got an error while it was running, as shown below:

```auto
===============> FIXED SOURCE TRANSPORT SIMULATION <===============

 Simulating batch 1
 WARNING: Particle 151 had a negative distance to a lattice boundary
 WARNING: Particle 376 had a negative distance to a lattice boundary
 WARNING: Particle 278 had a negative distance to a lattice boundary
 WARNING: Particle 76 had a negative distance to a lattice boundary
 WARNING: Particle 326 had a negative distance to a lattice boundary
 WARNING: WARNING: Particle 101 had a negative distance to a lattice boundary
Particle 26 had a negative distance to a lattice boundary
 WARNING: Particle 1 had a negative distance to a lattice boundary
 WARNING: Particle 452 had a negative distance to a lattice boundary
 WARNING: Particle 354 had a negative distance to a lattice boundary
 WARNING: Particle 301 had a negative distance to a lattice boundary
 WARNING: Particle 401 had a negative distance to a lattice boundary
 WARNING: Particle 430 had a negative distance to a lattice boundary
 WARNING: Particle 130 had a negative distance to a lattice boundary
 WARNING: Particle 252 had a negative distance to a lattice boundary
 WARNING: Particle 51 had a negative distance to a lattice boundary
 WARNING: Particle 478 had a negative distance to a lattice boundary
 WARNING: Particle 227 had a negative distance to a lattice boundary
 WARNING: Particle 203 had a negative distance to a lattice boundary
 WARNING: Particle 176 had a negative distance to a lattice boundary
 WARNING: Particle 153 had a negative distance to a lattice boundary
 WARNING: Particle 187 had a negative distance to a lattice boundary
 WARNING: Particle 481 had a negative distance to a lattice boundary
 WARNING: Particle 328 had a negative distance to a lattice boundary
 WARNING: Particle 483 had a negative distance to a lattice boundary
 WARNING: Particle 454 had a negative distance to a lattice boundary
 WARNING: Particle 28 had a negative distance to a lattice boundary
 WARNING: Particle 404 had a negative distance to a lattice boundary
 WARNING: Particle 134 had a negative distance to a lattice boundary
 ERROR: Maximum number of lost particles has been reached.
Abort(-1) on node 0 (rank 0 in comm 0): application called MPI_Abort(MPI_COMM_WORLD, -1) - process 0

```

This is my script,  
[test.ipynb](https://openmc.discourse.group/uploads/short-url/fOnXLMSfbNTh2xwFjvGuCQxQZVr.ipynb) (165.3 KB)  
Looking forward to suggestions!  
Best regards.