creates energy for spectrum color plot
spectra = SW_EGRID(spectra, 'Option1', Value1, ...)
It creates a grid along energy and stores the requested correlation
function component(s) binned in energy using the grid.
Input:
spectra Input structure, contains calculated correlation functions.
Options:
component Selects which correlation function component to be binned in
energy. The possible options are:
'Sperp' bins the magnetic neutron scattering intensity
(<Sperp * Sperp> expectation value).
Default.
'Sab' bins the selected components of the spin-spin
correlation function. Letter a and b can be 'x',
'y' or 'z'. For example: 'Sxx' will convolute the
xx component of the correlation function with the
dispersion. xyz is the standard coordinate system,
see online documentation of sw.
'Mab' bins the selected components of the spin-spin
correlation function. Letter a and b can be 'x',
'y' or 'z'. For example: 'Mxx' will convolute the
xx component of the correlation function with the
dispersion. The coordinates here are in the
Blume-Maleev coordinate system, see below.
'Pab' bins the selected element of the polarisation
matrix. Letter a and b can be 'x', 'y' or 'z'. For
example: 'Pyy' will convolute the yy component of
the polarisation matrix with the dispersion. The
coordinates used are in the Blume-Maleev coordinate
system, see below.
'Pa' bins the intensity of the simulated polarised
neutron scattering, with inciden polarisation of
Pa. Letter a can be 'x', 'y' or 'z'. For example:
'Py' will convolute the scattering intensity
simulated for incident polarisation Pi || y. The
used coordinates are in the Blume-Maleev coordinate
system, see below.
'fName' where fName is one of the field names of the input
structure spectra. This field should contain a
matrix with size [nMode nHkl].
Any linear combination of the above are allowed, for example:
'Sxx+2*Syy' bins the linear combination of the xx component of
the spin-spin correlation function with the yy component.
Several cross section can be convoluted and stored
independently, if component is a cell array containing strings
each containing any linear combination of cross sections as
above, the cell array needs to have size [1 nCell].
Evect Vector, defined the center of the energy bins of the calculated
output, dimensions ar is [1 nE]. The energy units are defined
by the unit.kB property of the sw object. Default is
linspace(0,1.1*maxOmega,500).
T Temperature to calculate the Bose factor in units
depending on the Boltzmann constant (sw.unit.kB). Default
temperature is taken from obj.single_ion.T. The Bose factor is
includec in swConv field of the output.
sumtwin If true, the spectra of the different twins will be summed
together weighted with the normalized volume fractions. Default
is true.
modeIdx Select certain spin wave modes from the 2*nMagAtom number of
modes to include in the output. Default is 1:2*nMagAtom to
include all modes.
The Blume-Maleev coordinate system is a cartesian coordinate system
with (xBM, yBM and zBM) basis vectors as follows:
xBM parallel to the momentum transfer Q,
yBM perpendicular to xBM in the scattering plane,
zBM perpendicular to the scattering plane.
Output:
spectra contains the following additional fields beside the input:
swConv Stores the selected cross section binned along energy, size is
[nE nHkl]. Includes the Bose factor.
swInt Stores the selected cross sections for every mode, size is
[nMode nHkl].
T Input temperature.
component Cell that contains the input component selector strings.
Evect Input energy bin vector.
param All the other input parameters.
If 'component' parameter is a cell array or the spectra of multiple
twins are convoluted separately, swConv and swInt will be packaged into
a cell. The dimensions of the cell are [nConv nTwin].
Example:
spectra = sw_egrid(spectra,'component',{'Sxx+Syy' 'Szz'},'Evect',linspace(0,5,51));
The line will create an energy bin, with steps of 0.1 and bins the
spin-spin correlation function. Two different matrices will be
calculated, first using the sum of the Sxx and Syy components, second
will contain the Szz component of the correlation function.
See also SW.SPINWAVE, SW_NEUTRON.