MAXDIS

MAXDIS = [real] 

Default: MAXDIS

= 0.0 (switched off)

Description: This tag sets the maximum distance that an atom is allowed to travel (in Angstrom) between two ab-initio steps before the charge density is reset to atomic an atomic charge density.

---

At each ionic step, the maximum Cartesian displacement of any atom (using minimum-image convention) is compared to MAXDIS. If exceeded, the charge density extrapolation controlled by IWAVPR is skipped and atomic densities are used instead. Setting MAXDIS=0.0 disables this reset entirely.

MAXDIS is particularly important in on-the-fly machine learning force field (ML_MODE=train) calculations, where many machine-learning-driven ionic steps are executed between successive ab initio evaluations. This allows atoms to travel a considerable distance between two DFT calculations, making the charge density from the previous ab initio step a poor initial guess for the next one — potentially causing slow or problematic electronic convergence.

Related tags and articles

IWAVPR, IBRION, POTIM, ML_LMLFF, ML_MODE