Momentum-transfer vector for the calculation of the dynamic structure factor.
When this variable is set, a non-dipole field is applied, and an output file
ftchd is created (it contains the Fourier transform of the charge density
at each time). The type of the applied external field can be set by
an optional last number. Possible options are qexp (default), qcos,
qsin, or qcos+qsin. In the formulae below,
q is the momentum-transfer vector.
Options:
qexp:
External field is eiq⋅r.
qcos:
External field is cos(iq⋅r).
qsin:
External field is sin(iq⋅r).
qbessel:
External field is jl(q⋅r)Ylm(r).
In this case, the block has to include two extra values (l and m).