Re: possible minimum box size

[Jean-Noël Grad]

Dear Ahmad Reza,

The minimum box size can be calculated with the following formula:

```python
max_interaction_cutoff = min(system.box_l / 
system.cell_system.node_grid) - system.cell_system.skin * 
(system.cell_system.get_state()['n_nodes'] > 1)
```

If your polymer has dihedrals, divide this value by 2. Run the attached 
MWE with 1 or 2 MPI ranks to see the effect of the LJ cutoff and skin.

Best,
JN

On 2022-02-28 16:15, Ahmad Reza Motezakker wrote:
> Dear EspressoMD users,
>
> I have a system including 2 polymer chains. In the warm up stage, I
> face below error:
>
> Encountered errors during integrate: ERROR: number of cells 1 is
> smaller than minimum 8 (interaction range too large or min_num_cells
> too large)
>
> The polymers are made of 15 beads (sigma = 1). cut off radius is
> 2**(1/6). I have played with box size and skin and cut off to see what
> is happening but it only works with box size of 57. Could you please
> help me with that? I want to decrease the box size to the smallest
> possible size.
>
> Thank you very much,
>
> Ahmad Reza

mwe.py
Description: Text document