Errors about the forcefield ClayFF used in Discover and Forcite package of Materials studio

Hell, everyone,

    I want to simulate a molecular dynamics model of water and brucite surface. And I used ClayFF as the forcefield, which is proved to be applied in simulation brucite structure successfully. However, when I take a energy minimization after the model obtained, some errors occurred when using both Minimizer in Discover and Geometry Optimization in Forcite. I am new to MS, and don't know how to solve this problem.  I wish your answer.  The pictures in attachment is errors in Forcite and Discover, the last one is a model I built.

   Thanks a lot !!!

   Chirstopher