I just wonder that scattering angle in 2-d periodic target.
In pbcscavec.f90, I found that
! scattering angle is neither zero nor pi
! scattering plane is therefore defined by k_0 and k_s .
Why scattering angle is neither zero nor pi?
And I carried out with following ddscat.par
'RCTGL_PBC' = CSHAPE*9 shape directive
30.0 1.0 1.0 1.0 1.0 = shape parameters 1 - 5
BETA = 0.000
THETA= 30.000
PHI = 0.000
and I got the out file 'w000r000k000.sca' like that
Mueller matrix elements for selected scattering directions in Target Frame
theta phi Pol. S_11 S_12 S_21 S_22 S_31 S_41
30.00 180.00 0.00009 9.9946E-01 -8.9653E-05 -8.965E-05 9.995E-01 5.805E-23 5.528E-25
150.00 180.00 0.81600 1.3728E-05 -1.1202E-05 -1.120E-05 1.373E-05 1.161E-24 1.372E-26
Why scattering directions are theta=30 and theta=150?
I can't understand.
Please advise to me.