System enclosed between walls

To whom it may concern,

I’m trying to perform numerical simulations of a system enclosed between walls, where my simulation box is a cube from -10 to 10. In particular, I want to use wall-harmonics. To this aim, I define:

fix xwall_hi all wall/harmonic xhi 10 1e8 1.0 10 units box

fix xwall_lo all wall/harmonic xlo -10 1e8 1.0 10 units box

Also, I use these definitions for y and z directions. The boundary conditions where “non-periodic and fixed”. After that, I apply a

minimization, and I receive the following error:

ERROR on proc 0: Particle on or inside fix wall surface (…/fix_wall_harmonic.cpp:75)

Last command: minimize 1.0e-4 1.0e-6 100 1000

Our next step has been to create atoms in a subregion from -9 to 9 in the

following way:

region simulation_box block -10 10 -10 10 -10 10

create_box 1 simulation_box

region subbox block -9 9 -9 9 -9 9

create_atoms 1 random ${N} 73302 subbox

My idea was to put atoms far away from the walls and, then, all particles would be distributed all over the simulation box. However, I still have the same error. I do not understand what I am doing bad. Could someone tell me where I’m going wrong?

Thank you in advance.


Your fix wall commands have “units box” keyword added meaning the walls are placed at -10 and 10 angstroms (instead of “lattices” which you intended). Just remove the “units box” keyword.