Hi,

Simulations are performed using the MARTINI force field.

Frist, 300 polyethylene oxide (PEO) molecules are randomly positioned in an initial periodic box of size 51 angstroms/size.

Second, geometry optimization are performed, the parameters are listed below:

---- Geometry optimization parameters ----

Algorithm                       : Smart

Convergence tolerance:

  Energy                        : 0.001 kcal/mol

  Force                         : 0.5 kcal/mol/A

Maximum number of iterations    : 10000

External pressure               : 0 GPa

Motion groups rigid             : NO

Optimize cell                   : NO

---- Energy parameters ----

Forcefield                      : PEO-W

Electrostatic terms:

  Summation method              : Ewald

  Accuracy                      : 0.001 kcal/mol

  Buffer width                  : 0.5 A

van der Waals terms:

  Summation method              : Bead based

  Truncation method             : Cubic spline

  Cutoff distance               : 12 A

  Spline width                  : 1 A

  Buffer width                  : 0.5 A

The .txt show that " WARNING Convergence criteria are not satisfied. Calculation did not reach convergence."

If ignoring this, and continuing performing a dynamics simulation, the .txt show that "Dynamics calculation - Aborting dynamics. An unphysical integration step (>100 Angstroms) has been detected. Try reducing the time step or

relaxing the structure first."

The initial box and force field files are in the annex.

I need some assistance.