sknano.structures.compute_symmetry_operation

sknano.structures.compute_symmetry_operation(n, m, bond=None)

Compute symmetry operation \((\psi|\tau)\).

The symmetry vector R represents a symmetry operation of the nanotube which arises as a screw translation, which is a combination of a rotation \(\psi\) and translation \(\tau\). The symmetry operation of the nanotube can be written as:

\[R = (\psi|\tau)\]

Parameters:

n, m : int

Chiral indices defining the nanotube chiral vector \(\mathbf{C}_h = n\mathbf{a}_1 + m\mathbf{a}_2 = (n, m)\).

bond : float, optional

Distance between nearest neighbor atoms (i.e., bond length). Must be in units of Å. Default value is the carbon-carbon bond length in graphite, approximately \(\mathrm{a}_{\mathrm{CC}} = 1.42\) Å

Returns:

(psi, tau) : tuple

2-tuple of floats – \(\psi\) in radians and \(\tau\) in Å.