Circular dichroism for a fingers crossed dimer of gold nanorods • terms

Objective

This example compares the results of TERMS with a coupled-dipole approximation for the far-field properties of a chiral dimer of Au spheroids.

This TERMS simulation uses the following input file

ModeAndScheme 2 3 
MultipoleCutoff 5
Wavelength 400 800 400
Medium 1.7689 # careful: be consistent with external T-matrix

TmatrixFiles 1
"tmat_Au10x25_Nmax3.tmat" 

OutputFormat HDF5 cross_sections

# dimer, dihedral pi/4
Scatterers 2
TF1 0 -40 0.0 25 0.0 0.0 0.0  2.5
TF1 0  40 0.0 25 0.0 0.7853982 0  2.5

as well as a second simulation with only the electric dipole term,

ModeAndScheme 2 3 
MultipoleCutoff 5
Wavelength 400 800 400
Medium 1.7689 # careful: be consistent with external T-matrix

TmatrixFiles 1
"tmat_Au10x25_Nmax3.tmat" 


MultipoleSelections 1
MM2:1_EM2:1_ME2:1_EE1:1  blocks

OutputFormat HDF5 cross_sections_dip

# dimer, dihedral pi/4
Scatterers 2
TF1_S1 0 -40 0.0 25 0.0 0.0 0.0  2.5
TF1_S1 0  40 0.0 25 0.0 0.7853982 0  2.5

The T-matrix file was previously created with SMARTIES using these parameters

head -n14 smarties.m

clearvars

wavelength = 400:1:800;
epsilon=epsAu(wavelength);
medium=1.33;

% stParams.a=20; stParams.c=50;
% stParams.a=10; stParams.c=20;
stParams.a=10; stParams.c=25;
stParams.N=3; stParams.nNbTheta=40;

stOptions.bGetR = false;
stOptions.Delta = 0;
stOptions.NB = 0;

The coupled-dipole simulations were performed with a in-house implementation in Matlab, which we are in the process of documenting and porting to the Julia language at CoupledDipole.jl.

Orientation-averaged results

This average cross-sections and circular dichroism are in good agreement, especially when TERMS uses only the electric-dipole term.

Last run: 05 December, 2023