Treat: Phonon: DOS: compute gDOS from partials ?

[farhi]

Look into intensity pre-factor to compute the gDOS from the partials when used on a 4D S(q,w).

[farhi]

for partial DOS per atom 'i', see Reichardt Eq (2.9) p 4
see also: Schober JNR 2014 Eq (9.105)
g_i(hw) = sum_j |e_i,j|^2 delta(hw - hw_j(q))
i.e. we weight the DOS with polarisation vector norms per atom