paw-pbe at expanded pressures. As volume inceases, pressure increases as well!

Problems running VASP: crashes, internal errors, "wrong" results.


Moderators: Global Moderator, Moderator

Post Reply
Message
Author
akberta
Newbie
Newbie
Posts: 3
Joined: Tue Mar 15, 2005 8:35 pm
License Nr.: 20

paw-pbe at expanded pressures. As volume inceases, pressure increases as well!

#1 Post by akberta » Tue Oct 04, 2005 8:34 pm

Dear vasp users:

I have encountered a rather unusual behavior when using the vasp code. When running fixed volume runs with the paw-pbe pseudopotential, I have found that in the expanded pressure region as the volume increases, the pressure increases as well! (In the compressed pressure region, the pressure-volume relationship was correct -- as volume increased, pressure decreased. This non-physical behavior shows up only in the expanded pressure region) Clearly, this isn't physical, and I am wondering if there is a bug in the paw-pbe pseudopotentials at expanded pressures?

I have searched the forum, but have not seen any other reports of this behavior. We are using vasp.4.6.28 on Opteron 64-bit dual processor machines, compiled with the Intel Fortran 9.0 code.

I am using these pseudopotentials:
PAW_PBE O_s 07Sep2000, PAW_PBE Fe_pv 06Sep2000 and PAW_PBE Si 05Jan2001

Any advice would be greatly appreciated. Thanks!
Amy
Last edited by akberta on Tue Oct 04, 2005 8:34 pm, edited 1 time in total.

admin
Administrator
Administrator
Posts: 2921
Joined: Tue Aug 03, 2004 8:18 am
License Nr.: 458

paw-pbe at expanded pressures. As volume inceases, pressure increases as well!

#2 Post by admin » Wed Nov 16, 2005 1:33 pm

first of all, please carefully check if your basis set size is converged:
all data calculated on the basis of the stress tensors require very
high precision (set ENCUT to at least 1.3 * max(ENMAX) in INCAR)
as a hint for insufficient basis set size: the total drift in the forces should be smaller than the forces acting on the ions themselves (OUTCAR).
Last edited by admin on Wed Nov 16, 2005 1:33 pm, edited 1 time in total.

Post Reply