[ase-users] ASE made Pt(111) surface, cannot converge in VASP

[Zhang, Qiang]

Hi Protik Das,


3.98 should be right and I do not think it is the problem of ismear. I use the same INCAR for my previous Pt calculations, they converge well. Also for vacuum, reducing the vacuum (5 A) does not make the convergence better.


I used to make these using VESTA and it converge really quick. Now I just try to use ase since it is easier. I think I might just made some stupid mistake in the script which I do not realize or do not know. Thanks for help any way.


Sincerely,


Qiang Zhang

________________________________
From: Protik Das <protik77 at gmail.com>
Sent: Monday, June 19, 2017 1:28:50 PM
To: Zhang, Qiang; ase-users at listserv.fysik.dtu.dk
Subject: Re: [ase-users] ASE made Pt(111) surface, cannot converge in VASP

It seems like a vasp issue rather than ASE issue. Your POSCAR should be alright. Some comments regarding vasp:

1. You used 3.98 angstrom for the bulk lattice constant. Are you sure that is the optimized lattice constant for the theory level (LDA/GGA) you are using? If this is not, it might effect convergence. I would suggest doing a full relaxation of bulk Pt and then using that lattice constant to create surface.

2. When you used 15 angstrom as vacuum value, it basically adding 15 angstrom vacuum in each direction. That means you are adding 30 angstrom vacuum which may be little too large.

3. As Pt is a metal, you need to pay close attention to ISMEAR and SIGMA values. Take a look here: http://cms.mpi.univie.ac.at/vasp/guide/node124.html .



On Mon, Jun 19, 2017 at 6:39 AM Zhang, Qiang <zhang.5671 at buckeyemail.osu.edu<mailto:zhang.5671 at buckeyemail.osu.edu>> wrote:

Hello Protik Das,


I just try to relax this created surface POSCAR. It is not converging. Thanks for your time.


Sincerely,


Qiang Zhang

________________________________
From: Protik Das <protik77 at gmail.com<mailto:protik77 at gmail.com>>
Sent: Monday, June 19, 2017 2:09:52 AM

To: Zhang, Qiang; ase-users at listserv.fysik.dtu.dk<mailto:ase-users at listserv.fysik.dtu.dk>
Subject: Re: [ase-users] ASE made Pt(111) surface, cannot converge in VASP
What calculation are you doing? Did you relax your surface before these calculations?

On Sun, Jun 18, 2017 at 10:54 PM Zhang, Qiang via ase-users <ase-users at listserv.fysik.dtu.dk<mailto:ase-users at listserv.fysik.dtu.dk>> wrote:

Dear ASE users,


I use ase to to make a Pt(111) surface

from ase.build import fcc111
from ase.io<http://ase.io> import write
slab = fcc111('Pt', size=(3,3,4), a=3.98, vacuum=15.0)
#write('pt111.xyz<http://pt111.xyz>', slab)

slab.write('POSCAR', vasp5=True)

I use the POSCAR (fix the bottom two Pt layers) for VASP calculation, but it is take long time without converging. Is there something wrong with my script? Thanks for your time.


Sincerely,

Qiang Zhang

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--
Protik Das,
ECE Graduate Student,
LATTE (http://latte.ece.ucr.edu),
University of California, Riverside.
--
Protik Das,
ECE Graduate Student,
LATTE (http://latte.ece.ucr.edu),
University of California, Riverside.
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