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FitProcess

This page gives hints on how to fit the anharmonic part of a model in multibinit.

Introduction

The fit process implemented in multibinit is based on [Escorihuela-Sayalero2017]. The fit process of multibinit contains two main options:

  • Generate the list of symmetry-adapted terms
  • Select the best coefficients in the list with the fit process

In the first option, multibinit will generate a set of coefficients only if fit_generatecoeff is set to one. This generation is mainly parametrized by fit_rangepower and fit_cutoff. You can avoid the generation by providing a list of coefficients with the model_anharmonic.XML file (see multibinit help file).

Then, the fit process will select the coefficients one by one up to fit_ncoeff according to the procedure details in [Escorihuela-Sayalero2017]. This process requires to provide the training_set_HIST.nc list file (see multibinit help file)

Tutorials

The First lesson on Multibinit explains how to build a lattice model and to run a dynamics.

basic:

  • bound_factors FACTORS for Goal Function of Energy, Forces, and Stresses during bounding process
  • bound_penalty Goal Function penalty for determination of bounding coefficients
  • fit_anhastrain FIT ANHARmonic STRAIN coefficients
  • fit_coeff FIT anharmonic COEFFficients
  • fit_cutoff FIT CUT-OFF of the anharmonic phonon interaction
  • fit_dispterms FIT anharmonic Strain-Phonon COUPLING coefficients
  • fit_efs FIT on Energy, Forces, and or, Stresses
  • fit_factors FIT FACTORS for Goal Function of Energy, Forces, and Stresses
  • fit_generatecoeff FIT GENERATE anharmonic COEFFicient
  • fit_iatom FIT anharmonic terms around ATOM I
  • fit_initializedata FIT INITIALIZE DATA for the fit
  • fit_ncoeff FIT Number of COEFFicients
  • fit_ncoeff_per_iatom FIT Number of COEFFicients per Irreducible ATOM
  • fit_rangepower FIT RANGE POWER for the coefficients
  • fit_spc_maxs FIT Strain Phonon Coupling maximum Strain
  • fit_spcoupling FIT anharmonic Strain-Phonon COUPLING coefficients
  • fit_tolmsde FIT TOLerance on Mean Standard Deviation of the Energy
  • fit_tolmsdf FIT TOLerance on Mean Standard Deviation of the Forces
  • fit_tolmsdfs FIT TOLerance on Mean Standard Deviation of the Forces and Stresses
  • fit_tolmsds FIT TOLerance on Mean Standard Deviation of the Stresses
  • opt_factors FACTORS for Goal Function of Energy, Forces, and Stresses during optimization of coefficients
  • sel_efs Select on Energy, Forces, and or, Stresses

useful:

expert:

Selected Input Files

paral:

v8: