geometric optimization of PtSSe bilayer giving unsatisfactory results

[fakir_chand1]

Dear experts,
I tried optimizing PtSSe Bilayer Structure but results do not match previously reported and other software's results.
lattice constant is supposed to be 3.69 A according to reported work and other software but our results always give smaller lattice constant
i have attached input and output files
please help us know what we can do to make it better
many thanks,
team kurukshtera

[ahampel]

Dear fakir_chand1,

thank you for asking your question on the official VASP forum.

I had a look at your input files and tried to reproduce your calculation. I am not an expert on this particular material so I cannot judge what is a "correct" lattice constant. However, I can reproduce your resulting CONTCAR with a smaller in plane lattice vector 4.32 (first component of CONTCAR). I found a problem in your calculation related to your POTCAR file. The POSCAR information does not match the POTCAR file. Please check if you also got this warning in your std output when running the calculation:

Code: Select all

WARNING: type information on POSCAR and POTCAR are incompatible
POTCAR overwrites the type information in POSCAR
typ   2 type information:  S  Pd

In your POTCAR file is also an POTCAR for Pd, which is probably a mistake? Please confirm. If I setup a POTCAR for Pt S Se and rerun the structural optimization I obtain an in-plane lattice constant of 3.67, which is closer to what you expect. I run the optimization first for your set EDIFF=1e-5 setting for 30 steps, then copied CONTCAR to POSCAR and run with EDIFF=1e-8 which converged after a few steps. This should be a first step towards the correct result I hope.

Let me know if this solves your problem.

Best regards,
Alex H.

[fakir_chand1]

thank you alex
yes i got that exact warning
now i am trying with new POTCAR file without Pd atom

[ahampel]

Hi fakir_chand1,

okay let me know if this problem is resolved. Then we can close the issue.

Best,
Alex

[fakir_chand1]

thank you so much dear alex
that worked so well, my lattice constant and bandgap both came out correct
folks in kurukshetra are very greatful to you.
very thankful,
team kurukshetra