# help for m/12 LJ potentials

DEAR ALL,

I try to use the LJ potential as the following types:
U=e(A(s/r)^12-B(s/r)^m), m=4, 6,…
BUT, after I check the email list, I still have no idea about how to implement it in LAMMPS. Would you please give me some suggestions? Thanks!

best

DEAR ALL,
I try to use the LJ potential as the following types:
U=e(A(s/r)^12-B(s/r)^m), m=4, 6,...
BUT, after I check the email list, I still have no idea about how to
implement it in LAMMPS. Would you please give me some suggestions? Thanks!

you have to be more specific. where _exactly_ is your problem?

with the limited information there are only two suggestions:
- use tabulated portentials (i.e. pair_style table)
- create a variant of pair_ljcut.cpp/pair_ljcut.h

axel.

Hi, axel,

Thank you very much for you email.

Actually, I try to find how does the attractive force part effect the mechanical properties of glass. I don’t want to change the centers of the potentials, so I need adjust the A and B. FOR example： for 6/12 type, 2A=B=2 and 8/12 type, 2B=3A=6.

At first I need quenching the system to the glass state based on those potentials and then the mechanical properties.

best,

2011/4/27 Axel Kohlmeyer <[email protected]…33…24…>

2011/4/27 Guan Pengfei <[email protected]>:

Hi, axel,
Thank you very much for you email.
Actually, I try to find how does the attractive force part effect the
mechanical properties of glass. I don't want to change the centers of the
potentials, so I need adjust the A and B. FOR example： for 6/12 type, 2A=B=2
and 8/12 type, 2B=3A=6.
At first I need quenching the system to the glass state based on those
potentials and then the mechanical properties.

with tabulated potentials you can do whatever you want.

i would first do some tests with the 12-6 LJ and generate a potential table
for that and test it against the lj/cut pair style. you need to find
out the table
style and number of points that keep errors small.

once you know how to produce good table, you can generate LJ type
potentials to your liking as tables with the same settings and mess
around with parameters as much as you like.

axel.