In order to use DDSCAT to perform the specific calculations of interest to you, it will be necessary to modify the ddscat.par file. Here we list the sample ddscat.par file, followed by a discussion of how to modify this file as needed. Note that all numerical input data in DDSCAT is read with free-format READ(IDEV,*)... statements. Therefore you do not need to worry about the precise format in which integer or floating point numbers are entered on a line. The crucial thing is that lines in ddscat.par containing numerical data have the correct number of data entries, with any informational comments on the line appearing after the numerical data.
' =================== Parameter file ===================' '**** PRELIMINARIES ****' 'NOTORQ'= CMTORQ*6 (DOTORQ, NOTORQ) -- either do or skip torque calculations 'PBCGST'= CMDSOL*6 (PBCGST, PETRKP) -- select solution method 'GPFAFT'= CMETHD*6 (GPFAFT, BRENNR, TMPRTN, CONVEX) 'LATTDR'= CALPHA*6 (LATTDR, LDRISO, GOBR88, DRAI88) 'ALLBIN'= CBINFLAG (ALLBIN, ORIBIN, NOTBIN) 'NOTCDF'= CNETFLAG (ALLCDF, ORICDF, NOTCDF) 'RCTNGL'= CSHAPE*6 (FRMFIL,ELLIPS,CYLNDR,RCTNGL,HEXGON,TETRAH,UNICYL,UNIELL) 8 6 4 = shape parameters PAR1, PAR2, PAR3 1 = NCOMP = number of dielectric materials 'TABLES'= CDIEL*6 (TABLES,H2OICE,H2OLIQ; if TABLES, then filenames follow...) 'diel.tab' '**** CONJUGATE GRADIENT DEFINITIONS ****' 0 = INIT (TO BEGIN WITH |X0> = 0) 1.00e-5 = ERR = MAX ALLOWED (NORM OF |G>=AC|E>-ACA|X>)/(NORM OF AC|E>) '**** ANGLES FOR CALCULATION OF CSCA, G' 33 = ICTHM (number of theta values for evaluation of Csca and g) 12 = IPHM (number of phi values for evaluation of Csca and g) '**** Wavelengths (micron) ****' 6.283185 6.283185 1 'INV' = wavelengths (first,last,how many,how=LIN,INV,LOG) '**** Effective Radii (micron) **** ' 1. 1. 1 'LIN' = eff. radii (first, last, how many, how=LIN,INV,LOG) '**** 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) 1 = IWRKSC (=0 to suppress, =1 to write ".sca" file for each target orient. '**** Prescribe Target Rotations ****' 0. 0. 1 = BETAMI, BETAMX, NBETA (beta=rotation around a1) 0. 90. 3 = THETMI, THETMX, NTHETA (theta=angle between a1 and k) 0. 0. 1 = PHIMIN, PHIMAX, NPHI (phi=rotation angle of a1 around k) '**** Specify Scattered Directions ****' 0. 0. 180. 30 = phi, thetan_min, thetan_max, dtheta (in degrees) for plane A 90. 0. 180. 30 = phi, ... for plane B