[QE-users] Convergence with interstitials

[Tejas Ramakrishnan]

Hello everyone,

To study diffusion barrier using NEB, to prepare the initial and final states, I am performing "relax" calculations with interstitials inserted into a vc-relaxed pure bcc W cell structure.
I have used k-points, cut-offs and cells size after verifying the convergence, but with interstitial added, I am having issues.
I have tried "mv" and "mp" smearing options, and I am USPP pseuodopotentials. With pure cell, convergence is usually between 16 to 40 iterations.
I tried the possibility of W being magnetic, and spin polarization option as well.
With an interstitial atom added, it doesn't converge well. I have retried with finer k-point grids as well, but no luck.
With the interstitial setup, I realize that the cell has odd number of valence electrons. Does the odd number of valence electrons in a cell matter?

I have searched through the mailing list archives, but can't seem to find any related posts on treating interstitials.

I have attached the input and output files, if someone could see what I am missing.

Regards,
Tejas R
PhD Student
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