ML AB

This file is used within the machine learning force field method. It contains the ab initio data from previous calculations: Bravais matrices, atom positions, energies, forces and stress tensors (the charge is also written out but only optionally used) . It is used for continuation runs (ML_ISTART=1 or ML_ISTART=2). The updated data is written to ML_ABN. Essentially the ML_AB and the ML_ABN files are the same and for continuation runs the ML_ABN file is just copied to ML_AB.

Here is a sample output how this file should look like:

1.0 Version
**************************************************
     The number of configurations
--------------------------------------------------
         10
**************************************************
     The maximum number of atom type
--------------------------------------------------
       1
**************************************************
     The atom types in the data file
--------------------------------------------------
     Si
**************************************************
     The maximum number of atoms per system
--------------------------------------------------
             64
**************************************************
     The maximum number of atoms per atom type
--------------------------------------------------
             64
**************************************************
     Reference atomic energy (eV)
--------------------------------------------------
 -0.785951000000000
**************************************************
     Atomic mass
--------------------------------------------------
   28.0850000000000
**************************************************
     The numbers of basis sets per atom type
--------------------------------------------------
        10
**************************************************
     Basis set for Si
--------------------------------------------------
          1     53
          2      3
          3     19
          4     62
          5     51
          6     41
          7     49
          8      3
          9     64
         10     56
**************************************************
     Configuration num.      1
==================================================
     System name
--------------------------------------------------
     Si_liquid
==================================================
     The number of atom types
--------------------------------------------------
       1
==================================================
     The number of atoms
--------------------------------------------------
         64
**************************************************
     Atom types and atom numbers
--------------------------------------------------
     Si     64
==================================================
     Primitive lattice vectors (ang.)
--------------------------------------------------
  11.0072130000000        0.000000000000000E+000  0.000000000000000E+000
  0.000000000000000E+000  11.0072130000000        0.000000000000000E+000
  0.000000000000000E+000  0.000000000000000E+000  10.1908520000000
==================================================
     Wycoff positions (Cartesian)
--------------------------------------------------
   0.69872000000000        2.47436000000000        7.82749000000000
   6.37825000000000        1.01296000000000        3.70012000000000
   5.47749000000000        3.63097000000000        7.54054000000000
   4.52326000000000        10.2439400000000        5.06801000000000
   ...                     ...                     ...
   ...                     ...                     ...
==================================================
     Total energy (eV)
--------------------------------------------------
  -302.800146000000
==================================================
     Forces (eV ang.^-1)
--------------------------------------------------
  0.256099000000000      -0.510102000000000       0.652442000000000
 -0.538669000000000       7.069000000000000E-002  3.899200000000000E-002
  0.189456000000000       0.566218000000000       2.230000000000000E-004
 -1.485015000000000       0.755044000000000       0.261758000000000
 -0.285376000000000      -0.341509000000000       -1.00031200000000
  ...                     ...                    ...
  ...                     ...                    ...
==================================================
     Stress (kbar)
--------------------------------------------------
     XX YY ZZ
--------------------------------------------------
  -26.3822000000000       -7.00984000000000       -31.6619300000000
--------------------------------------------------
     XY YZ ZX
--------------------------------------------------
   4.95694000000000        2.44523000000000        6.77740000000000

  ...
  ...
**************************************************
     Configuration num.      2
==================================================
...
...
...

Most of the entries should be self explanatory.
The data is stored for each configuration of the training data. The entries start with "Configuration num. n".
The first column of the entry "Basis set for atom" shows the number of the basis set for the given atom type. The second column shows which local reference configuration (atom) was chosen as a basis set.
The length of the system names are limited to 40 characters (same as for the structure names in the POSCAR file).

Important: The maximum size of the training structures ML_MCONF and the maximum size for the local configurations ML_MB in the INCAR file have to be set larger than the entries The number of configurations and The numbers of basis sets per atom type in the ML_AB file.