Recent Forum Posts
From categories:
page 1123...next »
draine (guest) 04 Aug 2017 16:15
in discussion DDSCAT / General discussion » polarization vector

1. The current release of DDSCAT is 7.3.2. DDSCAT 7.2 is no longer supported.
2. It is unclear what you mean by "cannot compile 2xxxryyykzzz.poln". Please clarify.

by draine (guest), 04 Aug 2017 16:15

Unfortunately, in its present form DDSCAT is not set up to treat the problem of a finite target near a semi-infinite slab.

For DDSCAT, the closest approximation to the posed problem would be to calculate the finite target placed at the surface of a rectangular block with the desired dielectric function representing the semi-infinite substrate. Use a block that is as large as you can afford, and repeat the calculation for different block sizes to see whether the results seem to be sensitive to the size of the block. This method is inelegant and unfortunately not very efficient; memory limitations will limit the size of the slab, given that the interdipole spacing d needs to be small enough to resolve the target geometry.

If your target happens to be a disk, you can use target option DSKRCTNGL. If your target happens to be a rectangular block, you can use target option RCTGLBLK2. If your target has another geometry, you can use target option FROM_FILE, and use your own software to prepare a file with the list of dipoles locations and compositions.

by draine (guest), 04 Aug 2017 16:13
draine (guest) 04 Aug 2017 15:58
in discussion DDSCAT / General discussion » Multilayered Ellipsoid

DDSCAT can work with complex structures. DDSCAT will calculate Muller matrix elements for the far-field, and can also do near-field calculations if desired. However, if the desired target geometry isn't one of the built-in target options, you will need to either (1) modify DDSCAT or (2) generate the list of "occupied" lattice sites (and compositions) using your own software tools, and use the FROM_FILE target option in DDSCAT to read in the list of occcupied sites. Option (2) is generally simplest since is doesn't require andy changes to DDSCAT.

The UserGuide describes how the input file for target option FROM_FILE should be formatted. There is a sample calculation in the examples/FROM_FILE directory.

Keep in mind that if one has a multilayer target, the interdipole spacing d should be small enough to resolve the thickness of the thinnest layer. One should always do a "resolution study" to verify that your results are not sensitive to your choice of interdipole spacing d.

by draine (guest), 04 Aug 2017 15:58

Dear Sir,
I am working with ellipsoid Nanomatryushka particles having two or more layers. I need to simulate values for the Muller Matrices for the kind of particles. Can I do it with DDSCAT? Can I model Fano Resonance with it?
If I need to modify the CONELLIPSE section for my use, how can I do it?
Regards,
Hirak

Multilayered Ellipsoid by hirakhirak, 04 Aug 2017 12:00

I Sm a new user of DDSCAT and I want to if it is possible to simulate a Target placed at the interface air/slab withing DDSCAT. If possible please can anyone guide?

Thank you

polarization vector
Arezu (guest) 15 Jun 2017 15:20
in discussion DDSCAT / General discussion » polarization vector

Hi

I am work with ddscat7.2. Now I want plot polarization direction in each point.
but I cant compile wxxxryyykzzz.poln .Could you help me.
Thank you in advance.

polarization vector by Arezu (guest), 15 Jun 2017 15:20
bysong (guest) 03 Jun 2017 04:10
in discussion DDSCAT / General discussion » CYLNDRPBC : 2-d periodic

Thank you very much.

I understand!!

by bysong (guest), 03 Jun 2017 04:10
drainedraine 02 Jun 2017 15:34
in discussion DDSCAT / General discussion » CYLNDRPBC : 2-d periodic

The angle theta described the direction of propagation of the radiation.
For 2-d periodic targets, the transmitted beam has the same theta as the incident beam.
For your example, the transmitted beam has theta=30.
In your example, S_11 for the transmitted beam appears to be very small.
The reflected beam is propagating at theta=180-30=150 deg
S_11 for this beam is the reflection coefficient, 0.816

As described in section 22.10 of the UserGuide, the ddscat distribution includes examples_exp/RECTCL_PBC as a "worked example". You may want to verify that you can repeat this calculation.

by drainedraine, 02 Jun 2017 15:34
bysong (guest) 02 Jun 2017 01:56
in discussion DDSCAT / General discussion » CYLNDRPBC : 2-d periodic

I guess that

If I set theta=30 in 2-d periodic target,

then the incident direction is theta=-30 and
the scattering direction is theta=30 and theta=150.

And scattering direction that theta=30 is reflected direction and
scattering direction that theta=150 is penetration direction.

Is it right?

by bysong (guest), 02 Jun 2017 01:56
bysong (guest) 02 Jun 2017 01:36
in discussion DDSCAT / General discussion » CYLNDRPBC : 2-d periodic

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.

by bysong (guest), 02 Jun 2017 01:36

1. The lines mentioned in the Makefile should read
MPI.f = $(MPI_f)
MPI.o - $(MPI_o)

i.e., there should be no space between the $ and (

2. When you compile and link, which of the following do you see used?
mpi_subs.f90 etc. on compilation and mpi_subs.o on linking,
or mpi_fake.f90 and mpi_fake.o ?

by drainedraine, 01 Jun 2017 15:52

Hello,

other codes using MPI have been successfully implemented in our system, therefore ours should be able to work too. Also, the job submission procedures are correctly implemented in our system. We have followed all the instructions in the USer Guide: we changed the PBCGS2 parameter to PBCGST in the file ddscat.par; also, in the "Makefile" we commented the initial parameters and commented the necessary ones:

DMPI = -Dmpi
MPI.f = $ (MPI_f)
MPI.o = $ (MPI_o)

Nevertheless, it still does not seem to work. Should we be changing any other parameters? If not, is there any parameter we stated incorrectly?

Thank you very much again.

by Javier (guest), 31 May 2017 11:21

Hello,

I study scattering using DDSCAT7.3.
I have some questions about CYLNDRPBC.
I want to make regolith using CYLNDRPBC, so I wrote shape parameter such like ::60.0 1.0 1 1.0 1.0 .

Then, in the output file 'w000r000k000.sca', there are only two theta values(0, 180)
I want to (0~180)theta value.
How can I do?

CYLNDRPBC : 2-d periodic by bysong (guest), 22 May 2017 08:47

The first step would be to verify that MPI is installed and operational, and what the local "job submission" procedures are on your system (which will include telling MPI how many cores or cpus to use for the calculation).

Have you succeeded running any other code using MPI on your system?

by drainedraine, 17 May 2017 11:49

Hello!

I am executing ddscat as a part of a University Thesis and I am having trouble using MPI for parallel calculations. I have followed all the instructions in the User Guide, having changed all the parameters necessary in both files "ddscat.par" and "Makefile". Once compiled, I am having trouble making the code understand it has to separate itself in different cores: it keeps on calculating everything in a single node. How do I manage to tell the code to run separately? Is there a parameter I should change that I don't know about?

Thank you!

by Javier (guest), 17 May 2017 09:33

Is it possible to calculate the electric field to limit the total volume of nanoparticle plasmon resonance wavelength of not only the wavelength؟

JPBC is an internal variable used by DDSCAT: JPBC=1 for targets that are periodic in one direction, JPBC=2 for targets that are periodic in two directions.
For periodic targets (such as CYLNDRPBC), DDSCAT requires that the scattering directions be specified in the target frame (TFRAME).

Re: scattering directions by drainedraine, 07 May 2017 13:05
draine (guest) 07 May 2017 11:53
in discussion DDSCAT / Report errors » meet a problem? asking for help!

First — please use the current version: ddscat7.3.2
Section 29 of the UserGuide describes what to do.
When you run with NRFLD=1, ddscat will create binary files wxxxryyykzzz.poln
The program ddpostprocess can read these files and write out selected data, such
as the polarizations, in files that can be used by other software, such as VTK.
Please see section 30.1 of the UserGuide.
You may wish to modify DDPOSTPROCESS.f90 to better meet your needs — see section 30.2 of the UserGuide.

by draine (guest), 07 May 2017 11:53
Arezu (guest) 06 May 2017 15:58
in discussion DDSCAT / Report errors » meet a problem? asking for help!

I am work with ddscat7.2. I plot nearfield of nanoparticles. Now I want plot polarization direction in each point.
but I cant compile wxxxryyykzzz.poln .Could you help me

by Arezu (guest), 06 May 2017 15:58
page 1123...next »
Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-ShareAlike 3.0 License