Error Related to Water Evaporation Problem

Dear All,

I’m trying to simulate a system in which I’ve a chunk of water(h2o) molecules sandwiched between 2 long graphene layers while keeping one(lower) graphene layer as a flat and the other(upper) layer free to move. As a result, I’ve got a hump on upper layer due to the presence of the chunk of h2o molecules. Now, I’m trying to study the affect of removing the water molecules(from outer surface of the h2o chunk in multiple steps) on the geometry of that hump in the upper graphene layer. The script goes like this(Note: In this script I’m trying to remove the water molecules only one time to see whether it works or not; by finding coordination number of H atoms with them-self and then forming a group of those H atoms who are having less coordination number since atoms at outer surface will have lesser coordination number than the once on the inside followed by deleting them with delete_atom with mol yes)

Dear All,


By following above script, can anybody please help me to understand why

it's giving following error(it's deleting all the water molecules instead
of just at the surface having lower coordination number resulting in an
error related to usage of coulombic interaction in zero-charge system):


*Deleted 2496 atoms, new total = 4160*
*Deleted 1664 bonds, new total = 0*
*Deleted 832 angles, new total = 0*
*d**ump 1 g_H cfg 1 dump_*.cfg mass type xs ys zs c_1 *

*run 0*

*PPPM initialization ...*
* extracting TIP4P info from pair style*
*WARNING: Using kspace solver on system with no charge (../kspace.cpp:285)*
*ERROR: Could not compute g_ewald (../pppm.cpp:1288)*

I'm trying to use the overlap style of delete_atoms as well by assigning
Hydrogen as first group and Carbon as second group but that as well giving
me same error. Can anybody please give me idea where I'm wrong or working
example of evaporation of liquid based upon same algorithm.

​the problem is, that without any charged atoms in the system, there is a
problem with the code that estimates the gewald parameter automatically
from the convergence threshold and the real-space​ cutoff.
thus if you want to proceed without any charged particles, you must set

​so adding:

kspace_modify gewald ​0.29

should do the trick.

btw: for systems with a small number of charged particles, you may see some
speedup from using pppm/cg over pppm.