values of pressure and force to study IR

BD 2015-02-04

I need to calculate IR of adsorbate on CeO2(110).

I am optimizing clean surface.

How much should I choose for force threshold?

I used 0.005, but in my output the stress is almost -25kbar. Is it sufficient for phonon and IR?

I think I should give a value for force to get 0.0 pressure in output (castep file). Is it right?My version is MS6.0, and I use module CASTEP.