molecular dynamic error

i want calculate the aggregate behavior of asphaltene ,and it failed when i set 10 Angstrom as the cutoff ,1fs as the time step。

run the NPT MD ,it cannot work and with this warings:

Warning the calculated value of the energy may not be reliable,

as the charge groups are large relative to the cutoff.

Try reducing the charge group size or use a cutoff of at least 29 Angstroms.

when i change the cutoff for 30 Angstrom,and it failed as well。

Dynamics calculation - Aborting dynamics.

An unphysical integration step (>100 Angstroms) has been detected.

Try relaxing the structure with geometry optimization, reducing the time step,

reducing the temperature or a combination of these.

although l reduce the time step ,it cannot work 。geometry optimization was run before NPT MD。

wish for your replay