Band gap

ase.dft.bandgap.bandgap(calc=None, direct=False, spin=None, output='-', eigenvalues=None, efermi=None, kpts=None)

Calculates the band-gap.

Parameters:

calc: Calculator object

Electronic structure calculator object.

direct: bool

Calculate direct band-gap.

spin: int or None

For spin-polarized systems, you can use spin=0 or spin=1 to look only at a single spin-channel.

output: file descriptor

Use output=None for no text output or ‘-’ for stdout (default).

eigenvalues: ndarray of shape (nspin, nkpt, nband) or (nkpt, nband)

Eigenvalues.

efermi: float

Fermi level (defaults to 0.0).

kpts: ndarray of shape (nkpt, 3)

For pretty text output only.

Returns a (gap, p1, p2) tuple where p1 and p2 are tuples of indices of the valence and conduction points (s, k, n).

Example:

>>> gap, p1, p2 = bandgap(silicon.calc)
Gap: 1.2 eV
Transition (v -> c):
    [0.000, 0.000, 0.000] -> [0.500, 0.500, 0.000]
>>> print(gap, p1, p2)
1.2 (0, 0, 3), (0, 5, 4)
>>> gap, p1, p2 = bandgap(silicon.calc, direct=True)
Direct gap: 3.4 eV
Transition at: [0.000, 0.000, 0.000]
>>> print(gap, p1, p2)
3.4 (0, 0, 3), (0, 0, 4)