Training Sets

DFTFIT uses Ab-Inito calculation to guide the optimization of potentials along with measured properties. The goal is to make it easier for users to include vasp calculations in their potential fitting. Thus DFTFIT has support for reading VASP vasprun.xml, Quantum Espresso *.out, and Siesta *.xml output files. The parsers will read as many sets that contain the structure, energy, stress, and forces. These output files may be the result of a relaxation, SCF, of BOMD, etc. calculation. If DFTFIT does not have support for the output format that you supply please submit an issue. Additionally measured properties include: lattice_constants, elastic_constants, bulk_modulus, and shear_modulus.

Measured Properties

Recently DFTFIT has added support for experimental properties and other measured quantities. These include: lattice_constants, elastic_constants, bulk_modulus, and shear_modulus. In order to use one you must include a ground_state for an example see this input training file.

  • lattice constants (lengths)
  • elastic constants (voigt)
  • bulk modulus
  • shear modulus

Ab-Initio Training Sets

Example of training sets include:

  • equilibrium structure
  • displaced structures \(0.01 \unicode{x212B} - 0.04 \unicode{x212B}\)
  • deformed structures \(\pm\%2\) normal, \(\pm\%8\) shear
  • random perturbed structures \(0.04 \unicode{x212B}\)
_images/mgo-training-sets-goal.png

Be aware the DFT calculations that change the unit cell result in less accurate energy, stress, and forces. Thus an additional SCF calculation will be necessary.

In general a selector is used to get the input files.

  • selector.filename select a specific output filename of type
  • selector.fileglob select a specific set of output files that match glob of type.
  • selector.num_samples for each matching file choose num_samples with maximum separation

An example Siesta training set is included below.

version: v1
kind: Training
spec:
  - type: Siesta
    selector:
      filename: test_files/siesta/d1_li_20ev.xml
      num_samples: 3
  - type: Siesta
    selector:
      filename: test_files/siesta/d1_o_30ev.xml
      num_samples: 4
  - type: Siesta
    selector:
      filename: test_files/siesta/d1_ta_20ev.xml
      num_samples: 5

VASP

spec:
 - type: VASP
   selector:
     filename: test_files/vasp/vasprun.xml.mgo

Quantum Espresso

spec:
 - type: QE
   selector:
     filename: test_files/espresso/...

Siesta

spec:
 - type: Siesta
   selector:
     filename: test_files/siesta/d1_o_30ev.xml
     num_samples: 4