Hello, Sir

I am using DDA to calculate the optical properties such as absorption, scattering and extinction for "CONELLIPS" shape (Two -layers). I have no idea about CONELLIPS shape, this type of target geometry is in-built or not. I have only changed the target geometry-(ELLIPSOID to CONELLIPS) and the composition-(40 40 40 60 60 60 = shape parameters 1 - 6) and run the code for two different materials. After that, i got the error as given below:

Error: FATAL ERROR IN PROCEDURE: TARCEL

AX < BX

EXECUTION ABORTED

As per the UserGuide, the first three shape parameters are the lengths/d of the *outer* ellipsoid,and shape parameters 4,5,6 are the lengths/d of the *inner* ellipsoid.

Shape parameter 1 should be *larger* than parameter 4, parameter 2 larger than parameter 5, and parameter 3 larger than parameter 6.

Hence if you wish to do concentric spheres, you could set shape parameters 1-6 to

60 60 60 40 40 40

Daer Sir,

I have one more problem regarding the core-shell calculations, when we define the outer and inner size e.g. 21 21 21 20 20 20, it means that, there is 1 nm shell thickness with core size 20 nm. while we defining such parameter, these parameters also defining the dipole, So for this condition, the number of dipoles must be 10 ^ 4. But in our above considered case, the dipoles are very less ( 4 x 10 ^ 3) . therefore, i want to know that how we can define the relevance dipoles ?

I am waiting yours fruitful discussion.

I wish you ll reply as soon as possible.

Thanking You

sir,

I am using DDSCAT 7.3 code in LINUX and facing problem for calculating absorption cross section for core- shell nanorods. Please help me how i calculate effective radii , and also tell how shape parameter and effective radii are correlated with each other.

Dear Sir,

I ran the calculation for Q_scat values for conellips using 70 70 70 30 30 30 shape parameters. The calculation executed with normal termination but no Q_scat or Q_ext values were shown in qtable file.

Moreoever, I am not much clear about the shape parameters. I mean, in my calculations, how to decide the thickness of core and mantle in conellips?

Thanks in advance,

1. specifiying the outer (70d) and inner (30d) diameters obviously determines the thickness of the shell (20d).

2. if ddscat terminated without writing Q values into qtable, then it didn't terminate normally.

I suggest you examine whatever was written to "standard output" to determine the reason for the code terminated.

Dear Sir,

I have one more problem regarding the core-shell calculations, when we define the outer and inner size e.g. 21 21 21 20 20 20, it means that, there is 1 nm shell thickness with core size 20 nm. while we defining such parameter, these parameters also defining the dipole, So for this condition, the number of dipoles must be 10 ^ 4. But in our above considered case, the dipoles are very less ( 4 x 10 ^ 3) . therefore, i want to know that how we can define the relevance dipoles and effective size (radius) ?

I am waiting yours fruitful discussion.

I wish you ll reply as soon as possible.

Thanking You

The ddscat.par parameters 21 21 21 20 20 20 specify a target with outer sphere diameter 21d and inner diameter 20d (*not* 21nm and 20nm unless you happen to have d=1nm). A sphere with diameter 21d has N approx (4*pi/3)*(10.5)^3 approx 4800 dipoles. The shell thickness would be 10.5d-10d=0.5d.

The effective radius aeff (in physical units) is specified on a separate line of ddscat.par . The physical size of

d is then fixed by N*d^3=(4*pi/3)aeff^3 , where N is the total number of non-vacuum dipoles.

Please consult the UserGuide for further details.

in our case, shell thickness is 0.5d and number of dipoles ~ 4840 dipoles. We took the d ~ 2 , when setting the physical size i.e. N*d^3 = (4*pi/3)aeff^3. after putting the N = 4840 dipoles and d ~ 2 and the we find out the affective radius i.e. ~ 20 nm. So in case shell thickness will be 0.5*2 = 1 nm.

Sir, am i right ?

Thanking You.