spin_soc

This Spin3 keyword controls whether the descriptor can couple spin direction to the local spatial environment:

spin_soc <flag>

The flag can be 0 or 1 and defaults to 1. It is used only with spin_version 1.

Value	Rotational symmetry represented by the descriptor
0	independent rotations of positions and spins
1	joint rotations of positions and axial spin vectors (default)

With value 0, Spin3 retains only the separately spin-rotation-invariant subset. With value 1, it also includes scalar contractions between spin and spatial rank-1/rank-2 objects up to spin_l_max. The flag changes the descriptor’s allowed information flow; it does not impose a particular analytic SOC Hamiltonian.