Problem with variable command

Hi,

I'm a newcomer in this field. I have a system with two types of particles
in it. Type 1 particles are within a spherical/spheroidal volume whereas
there are only two type 2 particles outside the spherical/spheroidal
volume. There are interactions between 1-1 and 1-2 type. The interactions
contain a term which include the coordinates of both types of atoms. Can I
use variable command in this framework?

I'm giving the term for your convenience.

Force between type1 and type2=...exp
(-(coordinate_of_type1-coordinate_of_type2)/connstant)

how can I implement this force??

Best,

How is this different from a spherical potential for which lammps supports many different types including tabulation?
Axel.

How is this different from a spherical potential for which lammps supports
many different types including tabulation?
Axel.
--

Actually I am confused about my particular form of the force field.. For
a best thinking i am hereby defining the form of the force :

Fx=((x_type1(i)-x_type2)/(dist between
them))*[exp{-(x_type1(i)-x_type2)/L}-C]

where L,C are constant.
'dist between them' means the magnitude of the radius vector between
'i'th type1 particle and type 2 particle.

Now the concern is that I have to take summation over all possible 'i' to
count F_net(x).

How is it possible ?

Saikat

I have not idea since your description is confusing me and there is not enough information to tell whether you are not transliterating the math correctly, or not describing it well or just know very little about md and potentials.

Sorry.

Axel