Solvation Error

Hi all

I am a new comer to DS. I have been trying to run an RNA molecule through solvation with the following properties:

- explicit periodic boundry
- radius of sphere 20
- minimum distance from boundry 7
- orthorhombic shape
- add counterions on

the imput file is a 3D model of the RNA molecule

the run does not complete and comes up with the error: Solvation Size too Large

what does this mean and how can I fix it?

Thank you in advance!