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SpinW / spinw

SpinW Matlab library for spin wave calculation
http://www.spinw.org
GNU General Public License v3.0
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Investigate edge effects in resolution convolution in sw_instrument #170

Open RichardWaiteSTFC opened 5 months ago

RichardWaiteSTFC commented 5 months ago

Convolution in sw_instrument seems to produce edge effects (specifically a lower intensity at the edge and a greater than average intensity in the next column/row)

To reproduce: (1) Run this script

% setup model
FMchain = spinw;
FMchain.genlattice('lat_const',[3 8 8],'angled',[90 90 90],'spgr',0);
FMchain.addatom('r',[0 0 0],'S',1,'label','MCu1','color','blue');
FMchain.gencoupling('maxDistance',7)
FMchain.addmatrix('value', eye(3),'label','Ja','color','green')
FMchain.addcoupling('mat','Ja','bond',1);
FMchain.genmagstr('mode','direct', 'k',[0 0 0],'n',[1 0 0],'S',[0; 1; 0]);
FMspec = FMchain.spinwave({[0 0 0] [1 0 0], 11},'hermit',false); % , 'sortMode', true);

% powder average
modQ = 0:0.1:0.5
FMpowspec = FMchain.powspec(modQ,'Evect',0:0.5:6,'nRand',1e3,'hermit',false);
% set intensities to 1
FMpowspec.swConv(:,:) = 1;

% convolute with dQ
FMpowspec = sw_instrument(FMpowspec,'dQ',0.1, 'Ei', 20, 'thetaMin', 3.5);
modQ
FMpowspec.swConv

prints

modQ =

         0    0.1000    0.2000    0.3000    0.4000    0.5000

FMpowspec.swConv =

       NaN       NaN    1.0000    1.0000    1.0033    0.9967
       NaN       NaN    1.0000    1.0000    1.0033    0.9967
       NaN       NaN       NaN    1.0000    1.0033    0.9967
       NaN       NaN       NaN    1.0000    1.0033    0.9967
       NaN       NaN       NaN    1.0000    1.0033    0.9967
       NaN       NaN       NaN    1.0000    1.0033    0.9967
       NaN       NaN       NaN       NaN    1.0033    0.9967
       NaN       NaN       NaN       NaN    1.0033    0.9967
       NaN       NaN       NaN       NaN    1.0033    0.9967
       NaN       NaN       NaN       NaN       NaN    0.9967
       NaN       NaN       NaN       NaN       NaN    0.9967
       NaN       NaN       NaN       NaN       NaN       NaN
RichardWaiteSTFC commented 5 months ago

One can do this Q-convolution for multiple 1D cuts

modQ = [0:0.1:0.5, 4:0.1:4.5];
FMpowspec = FMchain.powspec(modQ,'Evect',ebin_edge,'nRand',1e3,'hermit',false);
FMpowspec.swConv(:,:) = 1;
FMpowspec = sw_instrument(FMpowspec,'dQ',0.1, 'Ei', 20, 'thetaMin', 3.5);
modQ
FMpowspec.swConv

prints

modQ =

         0    0.1000    0.2000    0.3000    0.4000    0.5000    4.0000    4.1000    4.2000    4.3000    4.4000    4.5000

spec.swConv = 

       NaN       NaN    1.0000    1.0000    1.0033    0.9967    0.9967    1.0033    1.0000    1.0000    1.0033    0.9967
       NaN       NaN    1.0000    1.0000    1.0033    0.9967    0.9967    1.0033    1.0000    1.0000    1.0033    0.9967
       NaN       NaN       NaN    1.0000    1.0033    0.9967    0.9967    1.0033    1.0000    1.0000    1.0033    0.9967
       NaN       NaN       NaN    1.0000    1.0033    0.9967    0.9967    1.0033    1.0000    1.0000    1.0033    0.9967
       NaN       NaN       NaN    1.0000    1.0033    0.9967    0.9967    1.0033    1.0000    1.0000    1.0033    0.9967
       NaN       NaN       NaN    1.0000    1.0033    0.9967    0.9967    1.0033    1.0000    1.0000    1.0033    0.9967
       NaN       NaN       NaN       NaN    1.0033    0.9967    0.9967    1.0033    1.0000    1.0000    1.0033    0.9967
       NaN       NaN       NaN       NaN    1.0033    0.9967    0.9967    1.0033    1.0000    1.0000    1.0033    0.9967
       NaN       NaN       NaN       NaN    1.0033    0.9967    0.9967    1.0033    1.0000    1.0000    1.0033    0.9967
       NaN       NaN       NaN       NaN       NaN    0.9967    0.9967    1.0033    1.0000    1.0000    1.0033    0.9967
       NaN       NaN       NaN       NaN       NaN    0.9967    0.9967    1.0033    1.0000    1.0000    1.0033    0.9967
       NaN       NaN       NaN       NaN       NaN       NaN    0.9967    1.0033    1.0000    1.0000    1.0033    0.9967