SPC/E water potential implementation

Dear lammps users,

I am setting up a small test case of NVT equilibrium of water ( 132 molecules ) in a domain size 54 x 27 x 27 angs.


  1. water model is spc/e ;

  2. pairs_style lj/cut/coul/cut

  3. using fix nvt and fix shake.

When the HH and OH interaction are set to non zero ( ie. eps,sig in pair_coeff are non zero),

then the fix nvt and fix shake seems to work: Temp fluctuates around set value of 300k; the pressure

fluctuates ( not yet equilibrium ). Please see output in section 1 below.

However, if the HH and OH interactions are set to zero for SPC/E simulation , then the

temp and press are now “-nan-” values.

Please see section 2 in output below.

The lammps code segment is in section 3 below.

I would appreciate any assistance.