[Pw_forum] Pressure along the z-direction of slab

[loc duong ding]

Dear Users and Developers, 

I am trying to cell relax a slab structure (along z axis). What I expect is the pressure along z-direction ( diagonal term in pressure tensor) should be zero.  However, I see the value is about -20 kbar. 

Could you help me to figure out there is any wrong in this case? 

I greatly appreciate to all your help. 

With best wishes, 

-----------------------------------------------
Dinh Loc Duong , Dr.
Sungkyunkwan Advanced Institute of Nanotechnology
Department of Energy Science
Sungkyunkwan University,
Suwon, 440-746, Korea 
Email: mambom1902 at yahoo.com, ddloc at skku.edu