Relax again from the last structure and you should get smaller residual stress. Otherwise, increase the cutoffs. Please, read this http://www.quantum-espresso.org/wiki/index.php/Methodological_Background#Stress
Stress smaller than 10 kbar in a solid generally have little effect. Eduardo Menendez Proupin Departamento de Qu?mica Fisica Aplicada Facultad de Ciencias Universidad Aut?noma de Madrid 28049 Madrid, Spain Phone: +34 91 497 6706 ---------- Mensaje reenviado ---------- From: bramha pandey <pandey.bra...@gmail.com> To: PWSCF Forum <pw_forum at pwscf.org> Cc: Date: Thu, 22 Mar 2012 19:08:56 +0530 Subject: [Pw_forum] Small value of stress at equilibrium (T=0,P=0) 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. -- -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120322/30ace243/attachment.htm