How to calculate the stress tensor ?

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fanghz · #1 Post by **fanghz** » Fri Oct 10, 2008 7:38 am

Hello everyone, I want to obtain liquid viscosity by the Green-Kubo relation through ab-initio molecular dynamics simulation. The Green-Kubo relation is an integration of stress autocorrelation function S(t), which reads S(t)=Pxy(t)*Pxy(0). But I have no idea how to calculate the off-diagonal component of the stress tensor Pxy. Can this stress tensor be directly given in the OUTCAR file ? or can it be derived from the forces acted on the atoms? If it could be, how to set the INCAR file (ISIF=?) ?
Any positive help will be appreciated! Thanks all!

#2 Post by **admin** » Fri Oct 10, 2008 12:29 pm

the off-diagonal elements of the sress tensor are given in OUTCAR if ISIF>2

fanghz · #3 Post by **fanghz** » Sat Oct 11, 2008 9:08 am

Well. Since I'm carrying out MD calculations, how about using ISFI=2 and ENCUT=1.3*ENMAX ? Is this setting safe to calculate the stress tensors correctly ?
<span class='smallblacktext'>[ Edited Sat Oct 11 2008, 11:10AM ]</span>

#4 Post by **admin** » Tue Oct 14, 2008 2:12 pm

please set PREC=Accurate in addition.