model = sqw_gen_hydrodynamics(p, w, {signal}) : Generalized Hydrodynamics model
iFunc/sqw_gen_hydrodynamics Generalized Hydrodynamics model with Rayleigh-Brillouin triplet
This model can be used to fit e.g. a spectrum with a central non dispersive
quasi elastic line (lorentizian shape) and two dispersive (e.g. acoustic)
Stokes and anti-Stokes lines. This model is suited for e.g dense fluids at
small Q momentum values.
This is a 1D model to fit the parameters at a given 'q' momentum value.
The second frequency moment is obtained from the model parameters as:
<w^2> = zs^2 + ws^2 - a0 [ (z0-zs)^2 + ws^2 ] = kT q^2/[m S(q)]
The S(q,w) at one momentum value is computed in its symmetrized expression
(so-called classical). To get the 'true' quantum S(q,w) definition, use e.g.
sqw = sqw_gen_hydrodynamics .* bose;
where the Temperature is then given in [x units]. If 'x' is an energy in [meV]
then the Temperature parameter is T[K]/11.6045
To add a 'background' use e.g.
sqw = sqw_gen_hydrodynamics + constant('Background');
or
sqw = sqw_gen_hydrodynamics + strline;
To convolute with a pseudo-Voigt or Gaussian instrumental line width, use e.g.
sqw = convn(sqw_gen_hydrodynamics, gauss)
or
sqw = convn(sqw_gen_hydrodynamics, pseudovoigt)
Reference:
U. Bafile, E. Guarini, and F. Barocchi, Phys. Rev. E 73, 061203 (2006)
E. Guarini et al, Phys. Rev. B 88, 104201 (2013)
Version: Nov. 26, 2018
See also iData, iFunc/fits, iFunc/plot, gauss, sqw_phonons, sqw_cubic_monoatomic, sqw_vaks
<a href="matlab:doc(iFunc,'Models')">iFunc:Models</a>
(c) E.Farhi, ILL. License: EUPL.