# [lammps-users] Gay-Berne potential parameters

Hi all,

I am just working on a system consisting of two types of particles with different shapes. The first kind is a simple sphere with radius one and the other one is an ellipsoid with radii 3 1 1. The potential I’m going to use is gayberne. I am confused setting the potential parameters. I have read the manual but I think it contradicts with lammps example “ellipse”. I don’t know what is the relationship between potential parameters and desired ellipsoid radii.

Let an ellipsoid have radii a b and c. Consider the following lines:

shape a b c

pair_coeff 1 * epsilon sigma x1 x2 x3 y1 y2 y3

How should I set epsilon, sigma, x1, x2 and x3 in order to apply the different radii of ellipsoid in potential?

M. Baghery

Hi all,

I am just working on a system consisting of two types of particles
with different shapes. The first kind is a simple sphere with radius
one and the other one is an ellipsoid with radii 3 1 1. The potential
I'm going to use is gayberne. I am confused setting the potential
parameters. I have read the manual but I think it contradicts with
lammps example "ellipse". I don't know what is the relationship
between potential parameters and desired ellipsoid radii.

Let an ellipsoid have radii a b and c. Consider the following lines:

shape a b c
...
pair_coeff 1 * epsilon sigma x1 x2 x3 y1 y2 y3

How should I set epsilon, sigma, x1, x2 and x3 in order to apply the
different radii of ellipsoid in potential?

i would rather say that _your_ example contradicts bother
the ellipse example and what is in the LAMMPS manual.

the syntax for shape is:

shape <type> <a> <b> <c>

i.e. it takes four arguments and similarly there are
no x1 x2 x3 y1 y2 y3 parameters for the pair_coeff
command. in my (up-to-date) version of LAMMPS the ellipsoid
example matches the documentation well.

what version of LAMMPS are you using?

cheers,
axel.