Dear All,
I want to use UFF to simulate the interaction between clay minerals and liquid solution. I used QEq to calculate the charge, however, I got the error message that "this periodic system bears a net charge (-159e) and the QEq calculation cannot be performed. Unable to calculate energy and gradients. Geometry optimization finished with an error condition". I specifically set the total charge of the whole system as zero. 
Could you please give me some suggestion about that?

Thank you.

Regards,
Jing