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Dear all,

Please let me know if this is true or not:
1) In a static run, basis set is complete
2) Even if basis set is complete and our structure is relaxed, the external pressure is NOT zero. This is because the limited ENCUT and EDIFF (tol in scf)
3) if no 2) is true, between ENCUT and EDIFF, which one is more important to make external pressure zero?

Thx.

1) basis set completeness has nothing to do with whether you do a static run or not, the quality of the basis set depends on the cutoffs (and the k-points) you use.
2) If the structure is completely relaxed, the pressure should go down to 0.
If the cutoff is insufficient, automatic volume relaxation might fail because the accuracy of the calculated stess tensors is too small (please have a look at accuracy.pdf of the VASP-workshop tutorials).
3) you need both, good basis sets and sufficient electronic convergence for each ionic step.