Output pressure stabilizes at a different pressure than the input (in npt ensemble, core-shell model of PbTiO3)

LAMMPS LAMMPS Mailing List Mirror
1

Dear all,

I am using the Lammps version “3 Aug 2016-ICMS”
I am facing a problem while simulating the core-shell model of PbTiO3,

When using NPT ensemble, if I restrain pressure to be isotropic, then the input and output pressure match. However, if I set the pressure to be either anisotropic or triclinic, then the output pressure deviates substantially, and consistently settles down at a value other than that given in the input.
I have attached the input file, the data file, and a graph showing the difference in pressure using the three different pressure restraints.

Please suggest what is going wrong here.

Thanks and Regards,
Badari

plot.png

PTO.in (2.04 KB)

PTO.xyz (33.7 KB)

2

Dear all,

I am using the Lammps version "3 Aug 2016-ICMS"
I am facing a problem while simulating the core-shell model of PbTiO3,

When using NPT ensemble, if I restrain pressure to be isotropic, then the
input and output pressure match. However, if I set the pressure to be either
anisotropic or triclinic, then the output pressure deviates substantially,
and consistently settles down at a value other than that given in the input.
I have attached the input file, the data file, and a graph showing the
difference in pressure using the three different pressure restraints.

does this only happen when using a core-shell based system?
have you tried without, i.e. just using non-polarizable system with
regular point charges only?

Please suggest what is going wrong here.

after confirming whether this is a behavior specific to core-shell
calculations, you should probably continue the discussion with the
principal developer of the core-shell package.

axel.

3

Dear Alex,

Thanks for your comments. I tried the same code on the example file of NaCl given in the core-shell package. In this case, there was no problem, and the output pressure and input pressure matched in all three cases of iso, aniso and tri.

I wanted to make sure that there is nothing wrong with my code here. If not, then there could be some problem with the core-shell package, and I’ll contact the developer.