pythtb.WFArray.position_hwf#

WFArray.position_hwf(pos_dir, mesh_idx, state_idx=None, hwf_evec=False, basis='wavefunction')[source]#

Eigenvalues and eigenvectors of the position operator in a given basis.

Parameters:

mesh_idx: array-like of int: Set of integers specifying the index of interest in the mesh.
pos_dir: int: Direction along which to compute the position operator.

Changed in version 2.0.0: Renamed from dir to pos_dir to avoid conflict with built-in Python function dir().
state_idx: array-like, optional: List of states to be included. If not specified, all states are included.

Changed in version 2.0.0: Renamed from occ. The band indices are not required to be occupied bands only. The default behavior is to include all bands, and the "all" option has been removed.
hwf_evec: bool, optional: Default is False. If True, return the eigenvectors along with eigenvalues of the position operator.
basis: {“orbital”, “wavefunction”, “bloch”}, optional: The basis in which to compute the position operator.

Returns:

hwfcnp.ndarray

Eigenvalues of the position operator matrix \(X\) (also called hybrid Wannier function centers). Length of this vector equals number of bands given in evec input array. Hybrid Wannier function centers are ordered in ascending order. Note that in general n-th hwfc does not correspond to n-th electronic state evec.

hwfnp.ndarray, optional

Eigenvectors of the position operator matrix \(X\). (also called hybrid Wannier functions). These are returned only if parameter hwf_evec=True.

The shape of this array is [h,x] or [h,x,s] depending on value of basis and spinful.

If basis = "bloch" then x refers to indices of Bloch states evec.
If basis = "orbital" then x (or x and s) correspond to orbital index (or orbital and spin index if spinful=True).