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ML_FF_IWEIGHT = [integer]
Default: ML_FF_IWEIGHT = 3 

Description: Flag to control the weighting of training data in the machine learning force field method.

The following cases for ML_FF_IWEIGHT are possible:

  • ML_FF_IWEIGHT=1: Unnormalized energy, force and stress training data are divided by the weights determined by the flags ML_FF_WTOTEN (eV/atom), ML_FF_WTIFOR (eV/Angstrom) and ML_FF_WTSIF (kBar), respectively.
  • ML_FF_IWEIGHT=2: The training data are normalized by using their standard deviations. The averaging is done over whole training data. The normalized energy, forces and stress tensor are multiplied by ML_FF_WTOTEN, ML_FF_WTIFOR and ML_FF_WTSIF, respectively. In this case the flags ML_FF_WTOTEN, ML_FF_WTIFOR and ML_FF_WTSIF are unitless quantities.
  • ML_FF_IWEIGHT=3: Same as ML_FF_IWEIGHT=2 but training data is divided into individual systems. The energy, forces and stress tensor for a system are normalized using the average of the standard deviations of each system in the training data.

Mind: For ML_FF_IWEIGHT=2 and 3 the weights are unitless quantities used to multiply the data, whereas for ML_FF_IWEIGHT=1 they have a unit and are used to divide the data by them. All three methods provide unitless energies, forces and stress tensors.

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