I would like to surround two interacting spherical nanoparticles, each of a layer of silica; can i do this using the function ''CONELLIPS'', if it is possible how can i do that, if not which function can i use.

Thanks for your help! ]]>

Please i need to know if it is possible to have the imaginary part of the scattered wave with DDSCAT. Please if it is possible how can i have it.

thanks for your help ]]>

I have two questions:

1. I'm using the "nSphere" target generation to produce a target without overlapping spheres. I'd like to include nearfield calculations to examine if there's any nearfield interaction between the spheres. For a single sphere, such as the ellipsoid nearfield example, the nearfield calculation extends the computational volume beyond an individual sphere, as specified in the ddscat.par file. However, I'm confused how this works for nSpheres, where dipoles are only placed at sphere locations. Would a nearfield calculation with fractional extensions of 0.5 in all directions expand the computational volume around each sphere or would it somehow expand the computational volume around the entire TUC? Assuming its the former, if I wanted to include sphere-sphere nearfield interactions, should I specify the fractional extension to include nearest neighbor spheres? Or, am I misinterpreting these things?

2. I've been trying to extract the Qrad and Qtorque from calculations. When I include everything (i.e. "DOTORQUE"), the qtable still doesn't include those values. What setting should I double check to make ddscat write the Qrad and Qtorque?

Thank you for the help!

-Matt

I am trying to calculate the Qabs of a target immersed in water with wavelength ranged from 300 nm to 700 nm. Since the refractive index will change with the wavelength frequency, how should I set the refractive index in DDSCAT.par? It seems I could only set a special number instead of variables changing with wavelength. Thanks very much! ]]>

I want to investigate the properties using shape parameter ONIONSHEL for three layers with the spherical shape.

So, as given in DDSCAT manual on page no. 21, if SHPAR1 =1, then we have to define NCOMP = 3.

Now, problem is that how to set the thickness or radius of first, second and third layers with shape parameter SHPAR1, SHPAR2, and SHPAR3?

Please give the example with setting the values SHPAR1, SHPAR2, and SHPAR3 to run the ddscat.par file.

I wish you will reply soon and explain it with depth.

Thanking You

Your Sincerely

Bhatia P. ]]>

Hello, I am new and learning to use DDSCAT 7.3. I am at first trying to reproduce results from Dr. Flatau’s 2-spheres model that are in contact with each other (APPLIED OPTICS / Vol. 32, No. 18 / 20 June 1993 ). I have tried to reproduce the data, but with no luck. First of all, my S11 and S22 values are the same. Also, when I plot and compare the points to the literature values, the forward scattering looks like it reproduces S11, whereas the backscattering looks more like S22 character. Please let me know if you have suggestions for me.

Here is my input file, and header of my shape.dat file.

Thank you,

Yohanna White

*

shape.dat:

>TARELL ellipsoidal grain; AX,AY,AZ= 32.0000 32.0000 32.0000

34512 = NAT

1.000000 0.000000 0.000000 = A_1 vector

0.000000 1.000000 0.000000 = A_2 vector

1.000000 1.000000 1.000000 = lattice spacings (d_x,d_y,d_z)/d

-15.50000 0.50000 0.50000 = lattice offset x0(1-3) = (x_TF,y_TF,z_TF)/d for dipole 0 0 0

JA IX IY IZ ICOMP(x,y,z)

1 -2 -4 -16 1 1 1

2 -1 -4 -16 1 1 1

3 0 -4 -16 1 1 1

4 1 -4 -16 1 1 1

5 -3 -3 -16 1 1 1

ddscat.par:

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

' Preliminaries '

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

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

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

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

'NOTBIN' = CBINFLAG (ALLBIN, ORIBIN, NOTBIN)

' Initial Memory Allocation '

100 100 100 = dimensioning allowance for target generation

' Target Geometry and Composition '

'FROM_FILE' = CSHAPE*9 shape directive

no SHPAR parameters needed

2 = NCOMP = number of dielectric materials

'm1.33_0.001' = name of file containing RI info

'm1.33_0.001' = name of file containing RI info

' 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 allowed '

300 = MXITER

' Interaction cutoff parameter for PBC calculations '

1.00e-5 = 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) '

6.283 6.2833 1 'LIN' = wavelengths (first, last, how many, how=LIN,INV,LOG,TAB)

' Refractive index of ambient medium'

1.000 = NAMBIENT

' Effective Radii (micron) '

10.000 10.000 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)

' 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. 0. 1 = THETMI, THET MX, 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 '

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

11 22 = indices ij of elements to print

' Specify Scattered Directions '

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

2 = NPLANES = number of scattering planes

0. 0. 180. 5 = phi, thetan_min, thetan_max, dtheta (in degrees) for plane 1

90. 0. 180. 5 = phi, thetan_min, thetan_max, dtheta (in degrees) for plane 2

I have been trying to run DDSCAT for some custom shapes (FROM_FILE), with the shape.dat files generated from a MATLAB code or from the nanoHUB DDA Convert tool using Blender shapes. These are always created with the shape center at (0, 0, 0). The extinction spectra appear correct, and the E-field intensities generally make sense, but I run into issues somewhere between running ddpostprocess and using MayaVi or Paraview to visualize.

Despite the shape being centered, the E-field intensity map is always off-center and the shape outlines are thus cut off at the edges since they lay outside the computational volume (as ddpostprocess tells me when I try to select tracks from one edge of my shape to the other). I tried to visualize the target.out VTR files on the same set of axes in Paraview, and it looks like the entire shape is somehow thrown off-center since it matches up with the E-field plot. In MayaVi, however, I can only seem to visualize each separately, and while the E-field is still off-center, the target shape appears complete and centered in the outline box. This doesn't seem to change regardless of what I use to create the shape.dat file or what I use to visualize the ddpostprocess output.

While I know I can get a more complete image by changing the fractional extension of calculation volume in ddscat.par, my main concern is that the tracks I specify in ddpostprocess.par will not be directly through the center of the target as desired, since the entire shape is offset by some amount. Does anyone have any insight on how to resolve this issue? Would the output point towards some error in shape generation, in writing ddscat.par, or in writing ddpostprocess.par?

Thanks,

Rahil U.

FATAL ERROR IN PROCEDURE: TARCYL

NAT.GT.MXNAT

]]>I am using DDSCAT 7.3 to calculate the orientationally-averaged values of *Q*_{abs}, *Q*_{sca} and <cos*θ*> of randomly-oriented soot aggregates interacting with monochromatic plane waves with specified polarization states. According to * User Guide for the Discrete Dipole Approximation Code DDSCAT 7.3*, DDSCAT allows the user to specify a general elliptical polarization state for the incident radiation, by specifying the (complex) polarization vector ${\hat e_{01}}$ (see §24). Moreover, if

(1) Assume that the incident plane wave has a specified polarization state represented by the following Jones vector:

(1)\begin{align} J = \left[ {\begin{array}{*{20}{c}} {{E_{0y}}{e^{{\text{ - }}i{\delta _y}}}} \\ {{E_{0z}}{e^{{\text{ - }}i{\delta _z}}}} \end{array}} \right] \Leftrightarrow \left\{ {\begin{array}{*{20}{c}} {J = \frac{1}{{\sqrt {E_{0y}^2 + E_{0z}^2} }}\left[ {\begin{array}{*{20}{c}} {{E_{0y}}} \\ {{E_{0z}}{e^{{\text{ - }}i\delta }}} \end{array}} \right]} \\ {\delta = {\delta _z} - {\delta _y}} \\ {\cos \beta = \frac{{{E_{0y}}}}{{\sqrt {E_{0y}^2 + E_{0z}^2} }}} \\ {s{\text{in}}\beta = \frac{{{E_{0z}}}}{{\sqrt {E_{0y}^2 + E_{0z}^2} }}} \end{array}} \right\} \Rightarrow J = \left[ {\begin{array}{*{20}{c}} {\cos \beta } \\ {s{\text{in}}\beta \cos \delta - is{\text{in}}\beta s{\text{in}}\delta } \end{array}} \right] \end{align}

where *E*_{0y} and *E*_{0z} are the amplitude of the two components of the electric field vector, while *δ*_{y} and *δ*_{z} are the phase of the two components of the electric field vector, **should we simply set ${\hat e_{01}}$ by specifying (0, 0) (cos β, 0) (sinβcosδ, - sinβsinδ) in ddscat.par ?**

(2) Assume that we simply set ${\hat e_{01}} = {\hat y_{LF}}$ and ${\hat e_{02}} = {\hat z_{LF}}$, and calculate the orientationally-averaged values of *Q*_{abs}, *Q*_{sca} and <cos*θ*> in the two orthonormal polarization states, **can we calculate the orientationally-averaged values of Q_{abs}, Q_{sca} and <cosθ> in an arbitrary incident polarization state, just based on the orientationally-averaged values of Q_{abs}, Q_{sca} and <cosθ> in the two orthonormal polarization states ?**

Qext | Qabs | Qsca | g(1)=<cos> | <cos^2> | Qbk | Qpha | |

JO=1: | 9.2037E-01 | 8.1852E-01 | 1.0185E-01 | 7.2936E-02 | 4.0114E-01 | 1.0141E-02 | 5.3381E-01 |

JO=2: | 9.2037E-01 | 8.1852E-01 | 1.0185E-01 | 7.2936E-02 | 4.0114E-01 | 1.0141E-02 | 5.3380E-01 |

I am wondering **if the data in the lines of JO=1 and JO=2 in the red box are the calculation results of Q_{abs}, Q_{sca} and <cosθ> in the incident polarization states ${\hat e_{01}}$ and ${\hat e_{02}}$, respectively ?**

It is highly appreciated if you would instruct me on these questions, and I am looking forward to your reply.

Sincerely yours

Ya-fei Wang

Thanks in advance!

]]>I have modelled a group of nanospheres grouped together almost in a straight line. Can I model the scattering properties such that results obtained from the first nanosphere would become an input for the second nanosphere and so on for the whole network?

Thanks,

Hirak ]]>

I'm running the code in Linux Mint platform. The computer has 16GB RAM, 8 cores & I also installed 'OpenMPI.' Please kindly help me.

Thanks

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