pyxtal.interface.dftb module

class pyxtal.interface.dftb.DFTB(struc, skf_dir, disp='D3', kresol=0.1, folder='tmp', label='test', prefix='geo_final', use_omp=False, scc_error=1e-06, scc_iter=500)

Bases: object

Modified DFTB calculator

Parameters:

• struc – ase atoms object

• disp – dispersion (D3, D30, TS, MBD))

• step – optimization steps (int)

• kresol – kpoint resolution (float)

• folder – (str)

• label – (str)

• use_omp – True/False

get_calculator(mode, step=500, ftol=0.001, FixAngles=False, eVperA=True, md_params=None)

get the ase style calculator

Parameters:

• mode – [‘single’, ‘relax’, ‘vc_relax’] (str)

• step – relaxation steps (int)

• ftol – force tolerance (float)

• FixAngles – Fix angles between lattice vectors

• eVperA – unit in eV/A

Returns:

ase calculator

run(mode, step=500, ftol=0.001, FixAngles=False, md_params=None)

execute the actual calculation

pyxtal.interface.dftb.DFTB_SCF(struc, skf_dir, kresol=0.1, folder='tmp', disp=None, filename=None)

DFTB SCF to get band structure

Parameters:

• struc – ase atoms object

• skf_dir

• kresol

• filename – band structure output

pyxtal.interface.dftb.DFTB_relax(struc, skf_dir, opt_cell=False, step=500, fmax=0.1, kresol=0.1, folder='tmp', disp='D3', mask=None, symmetrize=True, logfile=None, scc_error=1e-06, scc_iter=500, use_omp=False)

DFTB optimizer based on ASE

Parameters:

• struc – ase atoms object

• mode – [single, relax, vc_relax] (str)

• step – optimization steps (int)

• mask – apply constraints on strain

class pyxtal.interface.dftb.Dftb(restart=None, ignore_bad_restart_file=<object object>, label='dftb', atoms=None, kpts=None, slako_dir=None, **kwargs)

Bases: FileIOCalculator

This module defines a FileIOCalculator for DFTB+

http://www.dftbplus.org/ http://www.dftb.org/

Initial development: markus.kaukonen@iki.fi Modified by QZ to avoid the I/O load

check_state(atoms)

Check for any system changes since last calculation.

command = 'dftb+ > PREFIX.out'

discard_results_on_any_change = True

Whether we purge the results following any change in the set() method.

implemented_properties: List[str] = ['energy', 'forces', 'stress']

Properties calculator can handle (energy, forces, …)

read_eigenvalues()

Read Eigenvalues from dftb output file (results.tag). Unfortunately, the order seems to be scrambled.

read_electrons()

read number o electrons

read_energy()

If SCC is not converged, read the last step energy from test.out

read_fermi_levels()

Read Fermi level(s) from dftb output file (results.tag).

read_forces()

Read Forces from dftb output file (results.tag).

read_results()

all results are read from results.tag file It will be destroyed after it is read to avoid reading it once again after some runtime error

write_dftb_in(outfile)

Write the innput file for the dftb+ calculation. Geometry is taken always from the file ‘geo_end.gen’.

write_input(atoms, properties=None, system_changes=None)

Write input file(s).

Call this method first in subclasses so that directories are created automatically.

pyxtal.interface.dftb.make_Hamiltonian(skf_dir, atom_types, disp, kpts, scc_error=1e-06, scc_iter=500, write_band=False, use_omp=False)

Generate the DFTB Hamiltonian for DFTB+