ML_LFAST

ML_LFAST = [logical]
Default: ML_LFAST = .FALSE.

Description: This tag switches on the descriptors for refitting for the very fast execution mode within machine learning force fields.

This tag is only available in the development version of VASP.

This tag switches on the descriptors for the very fast execution mode. The force field first has to be refit with these descriptors, which results in the creation of an ML_FFN_FAST file. After obtaining ML_FFN_FAST, that file has to be copied to ML_FF and the fast code can be used in production runs (ML_MODE=RUN} or ML_ISTART=2).

To retrain the force field and obtain an ML_FFN_FAST file set the following:

ML_MODE=REFIT

or set:

ML_LFAST=.TRUE.
ML_ISTART=4

The speedup of the fast method compared to the regular method is increasing with increasing number of local reference configurations.

It should be noted that in the fast version no Bayesian error estimation is available.

Since the calculation time of the fast version is of the same order of magnitude as the timing for the output of the molecular-dynamics results, we advise decreasing the output frequency for molecular dynamics. This is controlled by the tag ML_OUTBLOCK. By default, it writes out all molecular-dynamics results at every molecular-dynamics step. Additionally, the calculation and output of the pair-correlation function is suppressed by ML_OUTPUT_MODE=0 as default.

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