[gmx-users] Addition of ions in vacuum simulations

[OZGE ENGIN]

Hi all,

I am simulating a charged peptide in vacuum. I want to neutralize my system by using genion command,and as expected it asks me a continuous solvent group for the replacement; however, I have no solvents. 

How can I add ions to my system if I am in vacuum? or Is it necessary to add ions while performing simulations in vacuum?

Thanks in advance

Ozge