The physical value of a_eff is specified in ddscat.par.

The shape of the ellipsoid, and the number of dipoles that will be used, is determined when you set parameters SHPAR_1, SHPAR_2, SHPAR_3 (=A,B,C)

]]>However, I just tried your solution and I got the exact same values for the Qext values in the qtable! What is happening?? Do you think I am just trying to make too small of a shape? I used the vtrconvert and paraview to look at my target, and it looks like an ellipsoid as I expect it should.

Any other ideas?

]]>The best example I can give to help troubleshoot my issue is this ellipsoid (ddscat.par file copied at the bottom). I intended to create an ellipsoid with dimensions 7x7x11 nm and approximately 10,000 dipoles. I want the Qext values over a wavelength range of 200-1000 nm. I have tried this file for theta=0, theta=90, theta=0-90 (with 10 angles), as well as 0-90 for beta and theta, all while holding all the other angles constant at 0.. and every time I get the exact same Qext values. Shouldn't I get different extinction values when I am looking at the ellipsoid head on versus when it is rotated 90 degrees so I am looking at the long edge? Do you notice anything I am missing or doing wrong or do you have any suggestions of what I might try to change??

I've tried making this larger (70x70x110) and I've tried with as many as 100,000 dipoles as well, never with any success at recognizing the longer edge. I am using version 7.3.1, but not the most recent version of it.

Thank you!!

' ========== Parameter file for v7.3 ==================='

' Preliminaries '

'NOTORQ' = CMDTRQ*6 (DOTORQ, NOTORQ) — either do or skip torque calculations

'PBCGS2' = CMDSOL*6 (PBCGS2, PBCGST, GPBICG, QMRCCG, PETRKP) — CCG method

'GPFAFT' = CMETHD*6 (GPFAFT, FFTMKL) — FFT method

'GKDLDR' = CALPHA*6 (GKDLDR, LATTDR, FLTRCD) — DDA method

'NOTBIN' = CBINFLAG (NOTBIN, ORIBIN, ALLBIN) — binary output?

' Initial Memory Allocation '

100 100 100 = dimensioning allowance for target generation

' Target Geometry and Composition '

'ELLIPSOID' = CSHAPE*9 shape directive

25 25 39.286 = shape parameters 1 - 3

1 = NCOMP = number of dielectric materials

'../diel/polystyeq' = file with refractive index 1

' Additional Nearfield calculation? '

0 = NRFLD (=0 to skip nearfield calc., =1 to calculate nearfield E)

0.0 0.0 0.0 0.0 0.0 0.0 (fract. extens. of calc. vol. in -x,+x,-y,+y,-z,+z)

' Error Tolerance '

1.00e-5 = TOL = MAX ALLOWED (NORM OF |G>=AC|E>-ACA|X>)/(NORM OF AC|E>)

' Maximum number of iterations '

1000 = MXITER

' Integration limiter for PBC calculations '

1.00e-2 = GAMMA (1e-2 is normal, 3e-3 for greater accuracy)

' Angular resolution for calculation of <cos>, etc. '

0.5 = ETASCA (number of angles is proportional to [(3+x)/ETASCA]^2 )

' Wavelengths (micron) '

200 1000 801 'LIN' = wavelengths (1st,last,howmany,how=LIN,INV,LOG,TAB)

' Refractive index of ambient medium '

1.0000 = NAMBIENT

' Effective Radii (micron) '

4.0691 4.0691 1 'LIN' = eff. radii (1st,last,howmany,how=LIN,INV,LOG,TAB)

' Define Incident Polarizations '

(0,0) (1.,0.) (0.,0.) = Polarization state e01 (k along x axis)

2 = IORTH (=1 to do only pol. state e01; =2 to also do orth. pol. state)

' Specify which output files to write '

0 = IWRKSC (=0 to suppress, =1 to write ".sca" file for each target orient.

' Specify Target Rotations '

0. 0. 1 = BETAMI, BETAMX, NBETA (beta=rotation around a1)

0. 90. 10 = THETMI, THETMX, NTHETA (theta=angle between a1 and k)

0. 0. 1 = PHIMIN, PHIMAX, NPHI (phi=rotation angle of a1 around k)

' Specify first IWAV, IRAD, IORI (normally 0 0 0) '

0 0 0 = first IWAV, first IRAD, first IORI (0 0 0 to begin fresh)

' Select Elements of S_ij Matrix to Print '

9 = NSMELTS = number of elements of S_ij to print (not more than 9)

11 12 21 22 31 33 44 34 43 = indices ij of elements to print

' Specify Scattered Directions '

'LFRAME' = CMDFRM (LFRAME, TFRAME for Lab Frame or Target Frame)

1 = NPLANES = number of scattering planes

0. 0. 180. 1 = phi, theta_min, theta_max (deg) for plane A