temperature control

Dear LAMMPS Users,

I am simulating liquid flow through a nanaochanel which is confined by two walls in y and z direction respectively. The flow is along with x direction and I divided the fluid atoms into two groups including fluid group 1 and fluid group 2, in x direction. And four walls are treated as six groups with different constant temperature(T1=300K<T2<T3<T4<T5<T6).

Simulation has two stages. Firstly, temperatures of six wall groups and fluid group 1 are controlled by using ‘fix temp/rescale’command respectively. And I only consider velocity in y and z direction when performing thermostat for fluid group 1. No body force is added to each fluid atom in fluid group 1.

In second stage, after running the input file for 80,0000 timesteps (timestep=1 fs). A body force 200X10-12N along with x direction is added to all fluid atoms in fluid group 1 and 2. In this stage, velocity in y and z direction for each fluid atom is only considered when calculating temperature. At the same time, thermostat is still conducted for fluid group 1 (300K) by using ‘fix temp/rescale’.

However, in stage 2, temperature for fluid group 1 is much higher than 300K around 5000K. I will appreciate if you can give me some suggestion. Thank you.

Best wishes,