[Pw_forum] Small value of stress at equilibrium (T=0,P=0)

[bramha pandey]

Dear all,
I am using AlN with zincblede structure using USPP (PBE xc).
After completing convergence test of ecut and k-point, i calculated the
equilibrium lattice constant(at T=0, P=0).
But i wondered if i put this equilibrium lattice constant in calculation i
got, small value of stress(-7.36kbar).
i know this is Pulay stress and think it may be zero (may be i am wrong if
so please correct me) at equilibrium but here it is not the case.
i want to know whether this will affect the other property like bulk
modulus, lattice constant calculation etc at different pressure and
temperature.
How can i fix it.
Your valuable comment is highly aappriciable.

-- 
Thanks and Regards
Bramha Prasad Pandey
GLA University, Mathura.
INDIA.
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