band_structure: evaluates a 4D S(q,w) model along specified k-path / bands
band_structure(f, kpath, w, options)
The k-path can be given as a cell containing 3-values (HKL) vectors, or
a n x 3 matrix, each row being a HKL location.
The energy range can be entered as a vector, or a [min max] pair.
Refer to https://en.wikipedia.org/wiki/Brillouin_zone and
http://lamp.tu-graz.ac.at/~hadley/ss1/bzones/ to get the standard
points in the Brillouin zone.
The bands intensity is computed along the path. For neutron scattering,
as all standard points in the Brillouin zone are centered around 0 and
the intensity is proportional to |Q.e|^2, all transverse modes are extinct.
To get the proper band intensity around a given Bragg peak G, the k-path
should be shifted by G.
band_structure(f);
plots the dispersion curves following the BZ points for the
crystal spacegroup, and using the maximum excitation energy.
[S,k] = band_structure(...)
returns the dispersion curves data set (iData), and the k-path used.
When the command is followed by ';' or options contains 'plot', a plot is
generated.
Example:
S = band_structure(sqw_cubic_monoatomic, '', [0 10]); plot(log10(S));
S = sqw_phonons('POSCAR_Al','emt','metal'); band_structure(S);
input:
f: a 4D HKLE model S(q,w) (iFunc)
path: a list of k-locations given as a cell/array of HKL locations (cell or matrix)
can also be 'Cubic','Hexagonal','Trigonal','Tetragonal','Orthorhombic',
'Monoclinic','Triclinic','fcc','bcc'
can also be given as a list of BZ points, such as:
{'Gamma' 'K' 'M' 'Gamma' 'A' 'H' 'L' 'A' }
which are then defined according to the space group, e.g:
f.UserData.properties.spacegroup_number
can be given as a list of HKL locations, such as {[0,0,0],[1,1,1],[1,1,0]}
or as an array e.g. [0 0 0 ; 1 1 1 ; 1 1 0 ; 0 0 0 ; 0 0 1]
The path can also be given as a Bragg peak location, e.g. [0 0 1] to compute
the dispersion around that location using the default K-path in the BZ.
when not given or empty, this is guessed from the crystal spacegroup.
w: a vector of energies (4-th axis) for which to evaluate the model (double)
can also be given as Emax, or [ Emin Emax ]
when not given or empty, the maximum excitation energy is used.
options: plotting option (string). Can contain 'plot' 'THz','cm-1','meV'.
The 'plot' option also displays the density of states, when available.
The 'newplot' option does the same but opens a new figure instead of
re-using an existing one.
output:
S: the dispersion W(HKL) computed along the path (iData)
k: the k-path used to generate the dispersion curves (matrix, HKL list)
fig: figure handle generated when options contains 'plot' or no output.
Version: Nov. 27, 2018
See also sqw_cubic_monoatomic, sqw_sine3d, sqw_vaks, sqw_spinw
iFunc_Sqw4D/powder, <a href="matlab:doc(iFunc,'Models')">iFunc:Models</a>
(c) E.Farhi, ILL. License: EUPL.