[QE-users] Collapse of 316L stainless steel structure

[giuseppe.mattioli at mlib.ism.cnr.it]

Dear Yuvam Bhateja
Your input file seems correct. I can only suppose that you are using a 
badly unconverged ecutwfc. In a Fe supercell you start from highly 
symmetric atomic positions, so that forces on ions are symmetrized too 
and can't break initial symmetry. When you break the symmetry inserting 
Cr and Ni, then forces are not symmetrized anymore and are affected by 
the low ecutwfc value problem. the SSSP efficiency database suggest an 
ecutwfc value of 90 Ry for Fe PAW of the 0.3.1 atomic database, with a 
tremendous ecutrho of 1080 Ry... You may try to slightly randomize the 
position of Fe atoms in your all-Fe supercell to see if they recover 
their initial positions or go astray.

Gamma-only might be a too limited sampling of the 1BZ for a metal, too, 
but this should be a secondary problem.
HTH
Giuseppe

Il 2026-02-02 14:07 Yuvam Bhateja via users ha scritto:
> Greetings,
> 
>  I am trying to simulate 316L stainless steel structure with the FCC
> Fe unit cell as the base. My system has total 108 atoms and I have
> replaced Fe with Ni and Cr to match the composition of 316L steel.
> 
>  I have structurally optimized my Fe supercell before making the
> substitution. Everything is in order, however, my 316L keep collapsing
> inwards. Both relax and vc-relax is causing the same issue. It is not
> retaining the cuboidal shape but becoming distorted (towards becoming
> a sphere). I have tried different kinds of pseudopotentials: PBE,
> PBEsol with either PAW or USPP (NCSR). All of them are working for Fe
> supercell but none on the steel. I have tried to make the substitution
> fairly random and homogeneous.
> 
>  Can someone suggest what can I do to achieve a stable structure? I am
> attaching the input file and a snapshot of the relaxed structure.
> 
>  Thanks
>  Yuvam Bhateja
>  Department of Chemistry, Materials and Chemical Engineering "Giulio
> Natta"
>  Politecnico Di Milano
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