Hello Users,

I am simulating a series of ABA block copolymers. I would like to determine the average domain spacing or size, something similar to small angle x-ray scattering. I’ve been told I could calculate the density of atoms around a selected atom type with a varying distance but I was wondering if there was a standard method. It would be nice if I could figure out how to simulate a 1D SAXS pattern from my simulations.

Thanks for your help,

Casey

This sounds like a post-processing question,

not a LAMMPS question per se. I don't know how

to calculate the SAXS quantity you mention, so I would

start with the literature.

Steve

hello casey,

Hello Users,

I am simulating a series of ABA block copolymers. I would like to determine

the average domain spacing or size, something similar to small angle x-ray

scattering. I've been told I could calculate the density of atoms around a

selected atom type with a varying distance but I was wondering if there was

a standard method. It would be nice if I could figure out how to simulate a

1D SAXS pattern from my simulations.

the primary quantity that you are looking for is a radial distribution

function g(r). just pick an atom close to the center of mass for

each block and compute the g(r) for them you get the averaged

distance pattern. you can approximate the corresponding x-ray

pattern by taking the fourier transform of (g(r)-1).

please note that this simple approach assumes spherical symmetry.

anything more sophisticated requires consideration of relative

refractive indices and superposition of all particle type pair

combination and so on. there also are "brute force" direct

methods that are fairly effective when you program them to

run on graphics processors. if you need anything like this,

not just a simple approximation, then you need to follow

steve's suggestion and check out text books and publications

for what method exactly would be the best match for your needs.

cheers,

axel.